Power inverter

ABSTRACT

In a power inverter, a coolant passage is fixed to a chassis to cool the chassis; the chassis is divided into a first region and a second region by providing the coolant passage in the chassis; a power module is provided in the first region as fixed to the coolant passage; a capacitor module is provided in the second region; and the DC terminal of the capacitor module is directly connected to the DC terminal of the power module.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/188,630,filed Aug. 8, 2008, which claims priority under 35 U.S.C. §119 toJapanese Patent Application No. JP 2007-208505, filed Aug. 9, 2007, theentire disclosures of which are herein expressly incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power inverter that converts DirectCurrent (DC) power into Alternate Current (AC) power and vice versa.

2. Description of Related Art

The power inverter includes a function with which DC power supplied froma DC power supply is converted into AC power to be supplied to an ACelectricity load such as an electric rotating machine, and a functionwith which AC power generated by an electric rotating machine isconverted into DC power to be supplied to a DC power supply. To performthe conversion function, the power inverter further includes an invertercircuit which includes a switching device, and by repeating conductionoperation and interrupt operation with the switching device, the powerinverter converts from DC power to AC power or AC power to DC power.

Spike voltage is generated by inductance that exists in the circuitbecause the switching operation cuts off the current. For reducing thespike voltage, it is preferable to provide a smoothing capacitor and toreduce inductance at a DC circuit. A technology for controlling spikevoltage by reducing inductance is disclosed in Japanese Laid Open PatentPublication No. 2002-34268 (patent document 1). According to the patentdocument 1, inductance is reduced by shortening wiring between thesmoothing capacitor and the switching device so as to reduce the spikevoltage.

An in-car power inverter is provided with DC power from an in-carbattery and converts the DC power into three-phase AC power to besupplied to an electric rotating machine for vehicle, etc. As demand fortorque generated by an electric rotating machine for vehicle is largerthan that of early days, the power converted by a power inverter tendsto be larger. The in-car power inverter is used under high-temperatureenvironment in comparison to a power inverter for general industrialmachinery installed in factories. It is hence desirable for the in-carpower inverter to reduce heat generated by the power inverter itself incomparison to the general power inverter. Most of the heat generated bythe power inverter itself is the heat generated by the switching devicethat constitutes the inverter circuit. It is thus desirable to reducethe heat generated by the switching device as much as possible.

Heating value by the switching device increases at switching from theinterrupting state to the conducting state and at switching from theconducting state to the interrupting state. Therefore, it is desirableto reduce the heat at the switching operation. The first countermeasurefor reducing the heating value is to shorten switching operation time ofthe switching device. The second countermeasure is to lengthen intervalsbetween the switching operations for the switching device, in otherwords, to reduce the number of switching device operations per unittime. However, to extremely lengthen intervals between the switchingoperations for the switching device may reduce the accuracy of control.To greatly reduce the number of switching device operations per unittime has limit.

Japanese Laid Open Patent Publication No. 2007-143272 (patent document2) discloses a technology for shortening switching operation time of aswitching device of an inverter circuit to reduce heating value perswitching operation of the switching device by lowering inductance.

As described above, the technology disclosed in the patent document 1does not concern about reducing the heat at the switching operation ofthe switching device.

The patent document 2 discloses the technology for realizing lowinductance that results in reducing the heat value per switchingoperation of switching device. The patent document 2, however, has achallenge in reducing the heat value and reducing the size of the powerinverter because the power inverter, particularly the in-car powerinverter, does not have enough space around it.

As electric energy converted by the power inverter increases, equipmentstend to get bigger. So, it is preferable to minimize the volume of theequipments regardless of increase in the electric energy, in otherwords, for example, to increase the value of maximum convertibleelectric power per unit volume of the power inverter. For that, it isdesirable to achieve a balance between low inductance and reduction inthe size. Here, reduction in the size refers to maximization of thevalue of maximum convertible electric power per unit volume of the powerinverter.

SUMMARY OF THE INVENTION

A power inverter according to a 1st aspect of the present inventionincludes: a power module that comprises a plurality of switching devicesfor an upper arm and a lower arm that make up an inverter circuit, ametal board that releases heat generated by the plurality of theswitching devices, a DC terminal and an AC terminal; a smoothingcapacitor module that comprise a DC terminal; a gate drive circuit thatdrives the power module; a coolant passage through which coolant flows;and a chassis that houses the power module, the capacitor module, thegate drive circuit, and the coolant passage, wherein: the coolantpassage is fixed to the chassis to cool the chassis; the chassis isdivided into a first region and a second region by providing the coolantpassage in the chassis; the power module is provided in the first regionas fixed to the coolant passage; the capacitor module is provided in thesecond region; and the DC terminal of the capacitor module is directlyconnected to the DC terminal of the power module.

According to a 2nd aspect of the present invention, in the powerinverter according to the 1st aspect, it is preferable that the chassisis formed with an upper opening opened at an upper end and a loweropening at a lower end of the chassis; the first region exists betweenthe coolant passage and the upper opening; the second region existsbetween the coolant passage and the lower opening; the lower opening iscovered with a lower cover and the upper opening is covered with anupper cover; and a heat conduction passage is formed between the lowercover and the capacitor module.

A power inverter according to a 3rd aspect of the present inventionincludes: a chassis that comprises an upper opening at an upper end anda lower opening at a lower end of the chassis; an upper cover and alower cover that cover the upper opening and the lower openingrespectively; a power module that is housed in the chassis and comprisesa plurality of switching devices for an upper arm and a lower arm thatmake up an inverter circuit, a metal board that releases heat generatedby the plurality of the switching devices, and a DC terminal and an ACterminal; a smoothing capacitor module that comprises a DC terminal andsmoothes a DC voltage applied to the DC terminal of the smoothingcapacitor module, with the DC terminal of the smoothing capacitor moduleelectrically connected with the DC terminal of the power module; a gatedrive circuit, housed in the chassis, that drives the power module; anda coolant passage, on which the power module is mounted, that isprovided substantially parallel to the upper cover or the lower cover inthe chassis; wherein: the chassis is provided with a first regionbetween the upper cover and the coolant passage and a second regionbetween the lower cover and the coolant passage, by providing thecoolant passage inside the chassis; the power module is provided in thefirst region; a semiconductor module for auxiliaries and the capacitormodule are provided in the second region; and a space that links thefirst region and the second region is created between a side of thecoolant passage and the chassis, and the DC terminal of the capacitormodule and the DC terminal of the power module are electricallyconnected with each other through the space.

According to a 4th aspect of the present invention, in the powerinverter according to the 3rd aspect, it is preferable that the chassisis a substantially rectangular on an upper side; a water passage isformed in the coolant passage from a short side of the chassis, extendsalong a long side of the chassis, turns around, and returns alonganother long side of the chassis again to the short side; the space thatlinks the first region and the second region is formed between the waterpassage that extends along one of the long sides and the one of the longsides of the chassis; the power module is fixed on the water passagethat is bent and extends along the long sides of the rectangle; and theDC terminal of the power module is placed in the space and electricallyconnected with the DC terminal of the capacitor module through thespace.

According to a 5th aspect of the present invention, in the powerinverter according to the 4th aspect, it is preferable that the DCterminal of the capacitor module and the DC terminal of the power moduleare electrically and directly connected with each other through thespace.

According to a 6th aspect of the present invention, in the powerinverter according to the 1st to 5th aspects, it is preferable that thechassis is formed with a heat conduction member, and the capacitormodule and the gate drive circuit are cooled by coolant flowing throughthe coolant passage via the chassis.

According to a 6th aspect of the present invention, in the powerinverter according to the 1st to 5th aspects, it is preferable that thechassis is formed with a heat conduction member, and the capacitormodule and the gate drive circuit are cooled by coolant flowing throughthe coolant passage via the chassis.

According to a 7th aspect of the present invention, in the powerinverter according to the 1st to 6th aspects, it is preferable that theDC terminal of the capacitor module, that is electrically connected withthe DC terminal of the power module, comprises a positive busbar and anegative busbar, with the positive busbar and the negative busbarlaminated to form a laminated busbar; each of the positive busbar andthe negative busbar that make up the laminated busbar, comprises aconnection section; the connection section of the positive busbar andthe connection section of the negative busbar are bent in oppositedirections to each other such that internal surfaces of the positivebusbar and the negative busbar having been laminated are opened toprovide connecting surfaces at the connection sections; and the DCterminal of the capacitor module is electrically connected to the DCterminal of the power module via the connecting surface of the positivebusbar and the connecting surface of the negative busbar.

According to a 8th aspect of the present invention, in the powerinverter according to the 1st to 7th aspects, it is preferable that thecapacitor module includes: a capacitor case; a laminated busbar thatcomprises a positive busbar and a negative busbar sandwiching aninsulation material to form a laminated structure, and a planar sectionthat is an external surface of the laminated positive busbar andnegative busbar; a plurality of capacitor cells that are arranged inparallel on the planar section of the laminated busbar and a positiveterminal and a negative terminal of the capacitor cells are connected tothe positive busbar and the negative busbar respectively; and the planarsection of the laminated busbar and the plurality of the capacitor cellshoused in the capacitor case; wherein: the laminated busbar extends andprotrudes from the capacitor case, an end of the positive busbar and anend of the negative busbar that make up the protruded laminated busbarare bent in opposite directions to each other such that internalsurfaces at an the end of the positive busbar and the negative busbarhaving been laminated are opened to provide connecting surfaces; and theDC terminal of the capacitor module is electrically connected to the DCterminal of the power module via the connecting surface of the positivebusbar and the connecting surface of the negative busbar.

According to a 9th aspect of the present invention, in the powerinverter according to the 8th aspect, it is preferable that each of thecapacitor cells comprises a wound film conductor and is arranged suchthat an outer circumference surface of each of the capacitor cells facesthe planar section of the laminated busbar; and each of end faces of thecapacitor cells formed with the wound film conductor is electricallyconnected to the laminated busbar.

According to a 10th aspect of the present invention, in the powerinverter according to the 1st to 9th aspects, it is preferable that theDC terminal of the power module includes a laminated busbar made up of apositive busbar and a negative busbar; each of the positive busbar andthe negative busbar that make up the laminated busbar, comprises aconnection section; the connection section of the positive busbar andthe connection section of the negative busbar are bent in oppositedirections to each other such that internal surfaces of the positivebusbar and the negative busbar having been laminated are opened toprovide connecting surfaces at the connection sections; and the DCterminal of the power module is electrically connected to the DCterminal of the capacitor module via the connecting surface of thepositive busbar and the connecting surface of the negative busbar.

According to a 11th aspect of the present invention, in the powerinverter according to the 7th to 10th aspects, it is preferable that theDC terminal of the power module comprises a laminated busbar made up ofa positive busbar and a negative busbar; each of the positive busbar andthe negative busbar that make up the laminated busbar, comprises aconnection section; the connection section of the positive busbar andthe connection section of the negative busbar are bent in oppositedirections to each other such that internal surfaces of the positivebusbar and the negative busbar having been laminated are opened toprovide connecting surfaces at the connection sections; and theconnecting surface of the positive busbar and the connecting surface ofthe negative busbar of the DC terminal of the power module are directlyconnected to the connecting surface of the positive busbar and theconnecting surface of the negative busbar of the DC terminal of thecapacitor module, respectively.

According to a 12th aspect of the present invention, in the powerinverter according to the 1st to 11th aspects, it is preferable that thepower module comprises a AC terminal that is shaped in a plate andprotrudes from the power module; the AC terminal is provided with a holeinto which a protrusion or a pin provided in a case of the power moduleis inserted; and the AC terminal is sustained by the protrusion or thepin and the hole against outer vibration to the AC terminal fixed on thecase of the power module.

A power inverter according to a 13th aspects of the present inventionincludes: a coolant passage chassis that comprises an upper cover and alower cover; a power module, provided in the coolant passage chassis,that comprises a plurality of switching devices used for an invertercircuit, a metal board, shaped in a plate, that releases heat generatedby the plurality of the switching devices, a DC terminal, and an ACterminal; a smoothing capacitor module, provided in coolant passagechassis, that comprises a DC terminal which is electrically connectedwith a DC terminal of the power module; a gate drive circuit, providedin the coolant passage chassis, that drives the power module; and acooling unit that comprises a coolant passage provided in the coolantpassage chassis, wherein: by providing the coolant passage in thecooling unit chassis, a first region is created on one side of thecoolant passage and a second region is created on an other side of thecoolant passage; the metal board of the power module is fixed on thecooling unit in the first region; the capacitor module is provided inthe second region; a space that links the first region and the secondregion is created on a side of the coolant passage of the cooling unit;and the DC terminal of the capacitor module and the DC terminal of thepower module are electrically connected with each other through thespace.

According to a 14th aspect of the present invention, in the powerinverter according to the 13th aspect, it is preferable that the DCterminal of the capacitor module comprises a laminated busbar that ismade up of a positive busbar and a negative busbar, and that protrudesfrom the capacitor module; a capacitor cell is provided on one side ofthe laminated busbar in the capacitor module; and the laminated busbaroutside the capacitor module extends into the first region through thespace that links the first region and the second region, and isconnected to the DC terminal of the power module.

According to a 15th aspect of the present invention, in the powerinverter according to the 14th aspect, it is preferable that at an endof the DC terminal of the capacitor module, the positive busbar and thenegative busbar which make up the laminated busbar, are bent in oppositedirections to each other, and each of surfaces of the positive busbarand the negative busbar in the laminated busbar forms a connectingsurface; at an end of the DC terminal of the power module, the positivebusbar and the negative busbar which make up the laminated busbar, arebent in opposite directions to each other, and each of surfaces of thepositive busbar and the negative busbar in the laminated busbar forms aconnecting surface; and the connecting surfaces of the DC terminal ofthe capacitor module and the connecting surfaces of the DC terminal ofthe power module are connected with each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a control block diagram that shows a hybrid vehicle.

FIG. 2 is a circuit diagram that shows an electric system for driving avehicle.

FIG. 3 is an external perspective view of an entire configuration of apower inverter in accordance with an embodiment of the presentinvention.

FIG. 4 is an exploded perspective view of the entire configuration ofthe power inverter in accordance with the embodiment of the presentinvention.

FIGS. 5A to 5C show a chassis and illustrate flow of coolant in acoolant passage.

FIG. 6 is a bottom view of the chassis in which a power module thatrelates to the present embodiment is mounted.

FIG. 7 is a cross-sectional view of the entire configuration of thepower inverter shown in FIGS. 3 and 4 which relates to the presentembodiment.

FIG. 8 is a cross-sectional view of an essential part of the powerinverter shown in FIG. 7.

FIG. 9 is a left side view of the power inverter shown in FIG. 3.

FIG. 10 is a right side view of the power inverter shown in FIG. 3.

FIG. 11 is a rear view of the power inverter shown in FIG. 3.

FIG. 12 is a top perspective view of the power module which relates tothe present embodiment.

FIG. 13 is a bottom perspective view of the power module which relatesto the present embodiment.

FIG. 14 is a cross-sectional view of the power module which relates tothe present embodiment.

FIG. 15 is a plain view of the chassis in which the power module whichrelates to the present embodiment is mounted.

FIGS. 16A to 16C illustrate flow of electric current at turn-on state ofan IGBT which relates to the present embodiment.

FIG. 17 is a graph that shows waveforms of electric current and voltageat turn-on state of the IGBT which relates to the present embodiment.

FIGS. 18A and 18B illustrate flow of electric current at turn-off stateof the IGBT which relates to the present embodiment.

FIG. 19 is a graph that shows waveforms of electric current and voltageat turn-off state of the IGBT which relates to the present embodiment.

FIGS. 20A to 20C show schematic diagrams of an actual configuration ofthe series circuit of the upper and lower arms and its functions oreffects on an insulation substrate board mounted on metal board on thepower module which relates to the present embodiment.

FIG. 21 is a top view that shows the configuration of the power modulewhich relates to the present embodiment.

FIG. 22 is a perspective view that shows an external configuration witha filling material on a capacitor module which relates to the presentembodiment.

FIG. 23 is a top perspective view of a connecting structure of the powermodule and the capacitor module which relate to the present embodiment.

FIG. 24 is a view that shows flow of electric current at a connectionbetween a DC terminal and a capacitor terminal of the power module whichrelates to the present embodiment.

FIG. 25 is a top perspective view that shows an external configurationof the capacitor module which relates to the present embodiment withoutthe filling material.

FIG. 26 is a view that shows a pair of a negative terminal and apositive terminal of the capacitor module that make up a basic unit ofthe capacitor module which relates to the present embodiment.

DESCRIPTION OF PREFERRED EMBODIMENTS

A power inverter in accordance with embodiments of the present inventionwill be hereinafter described with reference to the drawings. Technicalproblems to be improved or solved and technologies for solving theproblems will be described first, with regard to the power inverter inaccordance with the present embodiment.

[Reduction in Inductance]

There are three measures to take for reducing inductance of electricalcircuits: firstly, reduction in inductance of a power module; secondly,reduction in inductance of a capacitor module; and thirdly, reduction ininductance of a connection circuit between the power module and thecapacitor module. It is most preferable to implement all the threemeasures. However, implementing one of the three has effect.Implementing two of the three has more preferable effect thanimplementing one of the three has.

The first measure, reduction in inductance of the power module, will bedescribed as follows. Semiconductor device chips used for an invertercircuit are incorporated in the power module. The power module isprovided with DC terminals for transferring DC electric power. A DCconductor between the DC terminals and the semiconductor devices has alaminated structure in which positive busbar and negative busbarsandwich insulation material. Inductance of the electrical circuitbetween the DC terminals and the semiconductor devices is considerablyreduced by the laminated structure.

Three series circuits are placed parallel inside the power module. Eachseries circuit includes semiconductor chips for each of upper and lowerarms of the inverter circuit. In embodiments hereinafter described,positive and negative terminals for supplying DC electric power to eachseries circuit are closely placed. Since the positive and negativeterminals for supplying DC electric power are closely placed, the flowof electric current is similar to a loop from the positive terminal tothe negative terminal through semiconductor chips for each of upper andlower arms. Since the electric current thus flows, eddy current isinduced to cooling a metal board of the semiconductor chips. Inductanceis reduced by the induction of the eddy current. That is, in embodimentshereinafter described, since the positive and negative terminals forsupplying DC electric power to each series circuit, which include upperand lower arms, are closely placed, inductance is reduced.

Positive and negative terminals of the series circuits which includesemiconductor chips for each of upper and lower arms are placed in themiddle between semiconductor chips for each of upper and lower arms. Thesemiconductor chip for the upper arm is placed at one side of positionof positive and negative terminals, while the semiconductor chip for thelower arm is placed at the other side of it. Electric current thussupplied from the middle between the semiconductor chips and the seriescircuits placed at both sides facilitate the loop-like flow of electriccurrent. Therefore, characteristics of reducing inductance is obtained.

In the embodiment hereinafter described, as described above, inductanceis reduced because of use of laminated busbars between DC terminals ofthe power module and the positive and negative terminals of the seriescircuits. Besides, inductance is reduced because of the loop-like flowof electric current through the series circuits. Inside inductance isthus reduced from DC terminals of the power module.

The second measure, reduction in inductance of the capacitor module,will be described as follows. The capacitor module is provided withlaminated busbars which include positive and negative busbars. Thelaminated busbars are provided with a plurality of capacitor cellsplaced parallel on a planar section. Electrodes at both ends of eachcapacitor cell are configured to be connected to either the positivebusbar or the negative busbar. This configuration enables inductance ofthe capacitor module to be reduced. In the embodiment described below,the laminated busbars which include the positive and negative busbarsprotrude from the capacitor module and make up DC terminals of thecapacitor module. Since the laminated busbars thus make up the terminalsof the capacitor module, inductance is reduced.

The third measure, reduction in inductance of the connection circuitbetween the power module and the capacitor module, will be described asfollows. In the embodiment hereinafter described, since terminals ofeach of the power module and the capacitor module have the laminatedstructure and are directly connected with each other, inductance of theconnection circuit between the power module and the capacitor module isreduced.

It is most preferable for the power module and the capacitor module tobe directly connected as mentioned above. Even if they are not directlyconnected with each other, however, inductance is reduced by connectingDC terminals of the power module and the capacitor module usinglaminated busbars which include positive and negative busbars.

It is preferable to reduce inductance of each connection in which thepower module and the capacitor module are directly connected or forwhich laminated busbars are used. In the embodiment hereinafterdescribed, the connection is configured as follows. Laminated busbars ofpositive and negative terminals are bent in the opposite direction toeach other. Internal surface of each laminated busbar is exposed to be aconnecting surface. The connecting surface is connected with otherconnecting surface of a counterpart. This configuration greatly reducesinductance of the connection and enables inductance between the powermodule and the capacitor module to be considerably reduced.

[Descriptions Related to Miniaturization of Power Inverter]

Efforts for miniaturization of the power inverter will be described byfollowing five respects. 1. Miniaturization of the power inverterthrough cooling the power inverter using both sides of a coolant passageplaced at the midpoint of a chassis of the power inverter. 2.Miniaturization of the power inverter by creating a space between theside of the coolant passage and the chassis for electrical connectionbetween the power module and the capacitor module. 3. Miniaturization ofthe power inverter through simplified wiring by parallel placement oftwo power modules along the coolant passage. 4. Structural improvementof the power module. 5. Structural improvement of the capacitor module.Each of the above efforts has effect. Combining these efforts bringsabout greater advantageous effects.

The first effort will be detailed as follows. In the embodimenthereinafter described, the coolant passage is placed at the midpoint ofa chassis of the power inverter for cooling the power inverter usingboth sides of the coolant passage. This configuration improves coolingefficiency for miniaturization. The power module is placeable on oneside of the coolant passage and the capacitor module is placeable on theother side. These placements reduce the volume necessary for cooling ofthe power module and the capacitor module and result in miniaturizationof the power inverter.

Other measures for miniaturization of the power inverter includeplacement of a gate drive circuit for driving semiconductor devices inthe power module on the side of the coolant passage where the powermodule is placed. This realizes simplification of connection between thepower module and a gate drive circuit.

Further measures for miniaturization of the power inverter includeplacement of the power module on one side of the coolant passage andplacement of an inverter device for auxiliaries on the other side. Theseplacements improve cooling efficiency and result in miniaturization ofthe power inverter. The inverter device for auxiliaries described aboveincludes an inverter device for a driving motor for an on-vehicle airconditioner and an inverter device for an oil pump motor. By placing aninverter device for auxiliaries and the capacitor module on the otherside of the coolant passage, the capacitor module is used as a smoothingcapacitor for an electric rotating machine for a vehicle and as asmoothing capacitor for the inverter for auxiliaries. Thus, circuitconfiguration is simplified and the power inverter is miniaturized.

The second effort will be detailed as follows. The coolant passage isprovided along one side of a substantially rectangular chassis. A hole,or a through-space, that links spaces on both sides of the coolantpassage is provided between the chassis and the side of the passageperpendicular to the above-mentioned one side of the chassis. Electricalcomponents provided on one side of the coolant passage and electricalcomponents provided on the other side of the coolant passage areelectrically connected with each other through the hole, or thethrough-space. Necessary electrical connection thus made through thehole, or the through-space, results in simplification of the connectionand miniaturization of power inverter.

The third effort will be detailed as follows. In the embodimenthereinafter described, the coolant passage is provided along one side ofthe substantially rectangular chassis. Two power modules are placedalong the coolant passage. The terminals on DC side and terminals on ACside of the two power modules are provided in the directionperpendicular to the coolant passage. This configuration enables thespace between the coolant passage and the chassis to be utilized forplacement of the terminals and results in miniaturization of the powerinverter. Since the terminals of the two power modules are placed in thedirection perpendicular to the two parallel power modules, they are lesslikely to interfere with each other. Thus, the power inverter isminiaturized. As described above, since the terminals on DC side of thetwo power modules are placed between the coolant passage and thechassis, the through-space that links both sides of the coolant passageis provided between the chassis and the coolant passage on the side ofthe terminals on DC side of the power module. The terminals on DC sideof the power module on one side of the coolant passage and the terminalson DC side of the capacitor module are connected through thethrough-space. Simplification of wiring, miniaturization of the powerinverter, and improvement in reliability are thus realized.

The fourth effort for miniaturization of the power module will bedetailed as follows. Each of the hereinafter-described two power modulesis provided with series circuits that include upper and lower arms ofthe inverter circuit which correspond to U-phase, V-phase, and W-phaseof three-phase AC. Since the series circuits are provided parallel,orderly placement of semiconductor chips of each of the series circuitsis realized.

In the embodiment hereinafter described, the semiconductor devices whichmake up the inverter circuit are fixed to a metal plate for coolingthrough insulating layer. The DC conductor that supplies DC electricpower to the power module is supplied on the semiconductor devices. Thatis, the metal plate for cooling is provided on one side of thesemiconductor devices and the DC conductor is provided on the other sideof the semiconductor devices. This configuration brings aboutminiaturization of the power module which results in miniaturization ofthe power inverter.

In the embodiment hereinafter described, terminals on AC side protrudefrom the power module and are used as AC output terminals of the powerinverter. This configuration reduces the number of components andresults in productivity improvement and miniaturization of the powerinverter.

The fifth effort, improvement of the capacitor module, will be detailedas follows. The capacitor module includes a plurality of capacitor cellsplaced on the positive and negative laminated busbars. Positive andnegative terminals of each capacitor cell are electrically connected tothe positive and negative busbars. Additional plurality of capacitorcells are placed on the laminated busbars on which the capacitor cellsare fixed. Small-sized large-capacity capacitor module is thus realized.Miniaturization of capacitor module brings about miniaturization ofpower inverter.

A film capacitor, which includes a film and a thin insulating memberwound or rolled up, is used for a capacitor cell. The film capacitor isfixed so that its outer circumference surface faces the surface of thelaminated busbars. This results in a miniaturized, vibration-resistant,and reliable capacitor module.

A plurality of capacitor cells are placed along the long side of thelaminated busbars. Electrodes of the capacitor cells are placed alongthe short side of the busbars. This configuration results in easierconnection between the capacitor cells and the busbars and improvesproductivity.

The following embodiment achieves further advantageous effects. Otherproblems to be solved by the embodiment will be described below.

[Reliability Improvement]

In the embodiment hereinafter described, the through-space is providedbetween the side of the coolant passage and the chassis for connectionbetween the power module and the capacitor module. Since the connectionis made through the through-space which is provided in a differentlocation from that the coolant passage is, it is less susceptible to thecoolant. This improves reliability.

Separation of solder fixing between the AC busbars and the power moduleboard caused by vibration of the motor generator is prevented byconnecting the AC busbars of U-phase, V-phase, and W-phase, which are ACoutput terminals of the power module, to a motor generator through pins.Reliability of the power inverter is thus improved. Workability andassembly productivity are also improved by pin coupling, an easycoupling method.

[Productivity Improvement]

A Chassis of cooling section is provided with a space for enclosing a DCconnecting terminal structure for connection between the power moduleand the capacitor, in addition to a coolant space for the coolantpassage for cooling a cooling fin of the power module. Covering theconnecting terminal structure with the chassis results in simplificationand miniaturization of the overall structure of the power inverter andimprovement in assembly productivity. Coolant in the coolant spacecontributes to capacitor cooling through the chassis of cooling section.

Connecting ends of the power module and the capacitor extend and aredirectly connected with each other without any particular connectingmembers. This configuration contributes to a simplified connectingterminal structure, miniaturization of the power inverter, andimprovement in both workability and assembly productivity.

[Improvement of Cooling Efficiency]

The power inverter in accordance with the present embodiment containsseries circuits of the upper and lower arms of the inverter deviceinside the power module (semiconductor module) which includes a coolingfin on one side, the power module inserted in cooling section, and thecooling fin directly cooled by the coolant. The power inverter employs,a laminated structure in which the power module and the smoothingcapacitor for a DC power supply are contained in the chassis of thecooling section where the coolant passage is provided, in other words, asandwich structure in which the coolant passage is sandwiched in betweenthe power module and the capacitor. Cooling efficiency is thus improvedto miniaturize the power inverter.

Coolant is poured into the coolant passage from the short side of therectangular chassis. The coolant passage extends along one of the longsides of the rectangular chassis and turns around to come back along theother long side of the rectangular chassis. The two power modules arecooled by the coolant passage in both directions along the both of thelong sides. This configuration improves cooling efficiency. Locations ofthe chips which make up the upper and the lower arms of the invertercircuit correspond to the both directions of the coolant passage. Thisconfiguration improves cooling efficiency. The improvement of coolingefficiency contributes to improvement of reliability and miniaturizationof the device. Above descriptions are related to advantageous effectsand problems to be solved in the embodiment of the present invention.The present embodiment will be detailed hereinafter.

The power inverter in accordance with the embodiment of the presentinvention will be hereinafter detailed with reference to the drawings.The power inverter in accordance with the embodiment of the presentinvention is applicable to hybrid vehicles and ordinary electricvehicles. The control configuration and the circuit configuration of thepower inverter to which the power inverter in accordance with theembodiment of the present invention is applied will be described withreference to the FIGS. 1 and 2. FIG. 1 shows a control block diagram fora hybrid vehicle. FIG. 2 is a circuit diagram that shows an electricsystem for driving a vehicle that includes the power inverter, a batteryand a motor generator. The power inverter includes an inverter unitprovided with series circuits of upper and lower arms and a controlunit, and a capacitor module that is connected to DC side of theinverter unit.

The power inverter in accordance with the embodiment of the presentinvention will be described with an example of an in-vehicle powerinverter of in-vehicle electric system to be mounted on a vehicle,particularly an inverter device for driving a vehicle that is used foran electric system for driving a vehicle in a challenging environment interms of installation and operation. The inverter device for driving avehicle is mounted on the electric system for driving a vehicle as acontrol device for controlling drive of electric machine for driving avehicle, converts DC electric power which is supplied from an in-vehiclebattery or power generating equipment into AC electric power, suppliesthe obtained AC electric power to the electric machine for driving avehicle, and thus controls drive of the electric machine for driving avehicle. Since the electric machine for driving a vehicle includesfunction as a generator, the inverter device for driving a vehicleconverts AC electric power generated by the electric machine for drivinga vehicle into DC electric power depending on operation mode. Theconverted DC electric power is supplied to the in-vehicle battery.

The configuration of the present embodiment is most appropriate forpower inverters for driving vehicles such as automobiles and trucks.However, it is also applicable to other power inverters including powerinverters for trains, ships, and airplanes, industrial power invertersused as a control device for electric machine which drives plant, orhousehold power inverters used as a control device for electric machinewhich drives household solar power system or consumer electronics.

In FIG. 1, a hybrid electric vehicle (HEV) 110 is an electric vehicleprovided with two systems for a driving vehicle. One of the systems isan engine system powered by an internal combustion engine 120. Theengine system is mainly used as a drive source for HEV. The other systemis an in-vehicle electric system powered by motor generators 192 and194. The in-vehicle electric system is mainly used as a drive source ora power generation source for HEV. Each of the motor generators 192 and194 is, for example, a synchronous machine or an induction machine,which is operated either as a motor or as a generator depending onoperation mode.

A front axle 114 is rotatably supported in a front part of the vehiclebody. A pair of front wheels 112 are provided on both ends of the frontaxle 114. A rear axle (not herein figured) is rotatably supported in arear part of the vehicle body. A pair of rear wheels (not hereinfigured) are provided on both ends of the rear axle. Even though afront-wheel drive system, in which main wheels powered by the engine areset to the front wheels 112 while driven wheels subordinated are set tothe rear wheels, is applied to the HEV in the present embodiment, arear-wheel drive system may be applied.

A front differential gear (Front DEF) 116 is provided in the center ofthe front axle 114. The front axle 114 is mechanically connected to anoutput side of the front DEF 116. An input side of the front DEF 116 ismechanically connected to an output shaft of a transmission 118. Thefront DEF 116 is a differential power transfer mechanism thatdistributes a rotational driving force with its speed reduced andtransferred by the transmission 118 to the front axle 114 in right andleft. Input of the transmission 118 is mechanically connected to outputof the motor generator 192. An input side of the motor generator 192 ismechanically connected to an output side of the engine 120 and output ofthe motor generator 194 via a power transfer mechanism 122. The motorgenerators 192 and 194 and the power transfer mechanism 122 arecontained in a chassis of the transmission 118.

The power transfer mechanism 122 is a differential mechanism made up ofgears 123 to 130. The gears 125 to 128 are bevel gears. The gears 123,124, 129, and 130 are spur gears. Power by the motor generator 192 isdirectly transferred to the transmission 118. An axis of the motorgenerator 192 is coaxial with the gear 129. This configuration makes thepower transferred to the gear 129 directly transferred to the input sideof the transmission 118, in the case when no electric power is suppliedto the motor generator 192.

When the gear 123 is driven by the engine 120, the power of the engine120 is transferred from the gear 123 to the gear 124, from the gear 124to the both of the gears 126 and 128, from the both of the gears 126 and128 to the gear 130, and lastly transferred to the gear 129. When thegear 125 is driven by the motor generator 194, rotation of the motorgenerator 194 is transferred from the gear 125 to the both of the gears126 and 128, from the both of the gears 126 and 128 to the gear 130, andlastly transferred to the gear 129. For the power transfer mechanism122, other mechanisms including a planetary gear mechanism may beapplied in place of the differential mechanism described above.

Each of the motor generators 192 and 194 is the synchronous machine withpermanent magnets in its rotor. Drive of the motor generators 192 and194 is controlled by inverter devices 140 and 142 that control ACelectric power supplied to armature coils of a stator of the motorgenerators 192 and 194. Since the inverter devices 140 and 142 areelectrically connected to a battery 136, electric power is transferablebetween the battery 136 and each of the inverter devices 140 and 142.

In the present embodiment, a first motor-generator unit made up of themotor generator 192 and the inverter device 140 and a secondmotor-generator unit made up of the motor generator 194 and the inverterdevice 142 are provided and selectively used depending on the state ofoperation. In other words, in the case of assisting drive torque whenthe vehicle is driven by the power of the engine 120, the secondmotor-generator unit is operated as a generating unit by the power ofthe engine 120 for generating electric power, and the firstmotor-generator unit is operated as a motor unit by the electric powergenerated by the second motor-generator unit. In the case of assistingvehicle speed when the vehicle is driven by the power of the engine 120,the first motor-generator unit is operated as a generating unit by thepower of the engine 120 for generating electric power, and the secondmotor-generator unit is operated as a motor unit by the electric powergenerated by the first motor-generator unit.

In the present embodiment, operating the first motor-generator unit as amotor unit by the electric power of the battery 136 enables the vehicleto be driven only by the power of the motor generator 192. In thepresent embodiment, the battery 136 is recharged by operating either thefirst motor-generator unit or the second motor-generator unit as agenerating unit by either the power of the engine 120 or wheels.

The battery 136 is used as a battery for driving a motor 195 forauxiliaries. The auxiliaries include, for example, a motor for drivingan air-conditioning compressor and a motor for driving a controlhydraulic pump. DC electric power is supplied from the battery 136 to aninverter device 43, converted into AC electric power by the inverterdevice 43, and supplied to the motor 195. The inverter device 43 isprovided with a similar function to that of the inverter devices 140 and142, and controls phase, frequency and electric power of AC supplied tothe motor 195. The motor 195 generates torque, for example, by supplyingAC electric power of leading phase to rotation of a rotor of the motor195. On the other hand, the motor 195 acts as an electric generator andoperates regenerative braking, by generating AC electric power oflagging phase. The control function of the inverter device 43 is similarto that of the inverter device 140 or 142. Since capacity of the motor195 is smaller than that of the motor generator 192 or 194, maximumconversion electric power of the inverter device 43 is smaller than thatof the inverter device 140 or 142. Circuit configuration of the inverterdevice 43, however, is basically the same as that of the inverter device140 or 142.

The inverter devices 140, 142, and 43, and a capacitor module 500 are inan electrically close relation between themselves, and commonly requiremeasures against the heat and miniaturization of the devices. The powerinverter detailed below thus contains the inverter devices 140, 142, and43, and the capacitor module 500 in its chassis. This configurationrealizes a small and reliable device.

Containing the inverter devices 140, 142, and 43, and the capacitormodule 500 in the single chassis have advantageous effects insimplification of wiring and noise filtering. Inductance of theconnection circuits between the capacitor module 500 and each of theinverter devices 140, 142, and 43 can also reduced. Spike voltage andthe heat are also reduced. Heat generation is reduced and radiationefficiency is thus improved.

Electric circuit configurations of the inverter devices 140, 142, and 43will be described below with reference to FIG. 2. The inverter devices140, 142, and 43 have similar configurations, advantageous effects, andfunctions in common. In the following explanation, therefore, theinverter device 140 will be described as a representative example.

A power inverter 200 in accordance with the present embodiment isprovided with the inverter device 140 and the capacitor module 500. Theinverter device 140 is provided with an inverter circuit 144 and acontrol unit 170. The inverter circuit 144 is provided with a pluralityof upper and lower arms series circuits 150 including an IGBT (insulatedgate bipolar transistor) 328 and a diode 156 which operate as the upperarm and an IGBT 330 and a diode 166 which operate as the lower arm.Three of the upper and lower arms series circuits 150, 150, and 150 areillustrated in FIG. 2. The inverter circuit 144 is connected to themotor generator 192 at midpoints of the upper and lower arms seriescircuits 150 (intermediate electrodes 169), which are connected to ACelectric power lines (AC busbars) 186 of the motor generator 192 via ACterminals 159. The control unit 170 includes a gate drive circuit 174which drives and controls the inverter circuit 144, and a controlcircuit 172 which supplies control signal to the gate drive circuit 174through a signal line 176.

The IGBTs 328 and 330 of the upper and lower arms are switching powersemiconductor devices which are operated in response to drive signalsoutput from the control unit 170 and convert DC electric power suppliedfrom the battery 136 into three-phase AC electric power. The convertedelectric power is supplied to the armature coil of the motor generator192. As described above, the inverter device 140 converts three-phase ACelectric power generated by the motor generator 192 into DC electricpower.

As shown in FIG. 1, the power inverter 200 in accordance with thepresent embodiment is provided with the inverter devices 140, 142, and43, and the capacitor module 500. As described above, since the inverterdevices 140, 142, and 43 have circuit configurations in common, theinverter device 140 is mentioned as a representative example and theothers are not mentioned.

The inverter circuit 144 is made up of a three-phase bridge circuitwherein the upper and lower arms series circuits 150, 150, and 150 forthree phases are electrically connected in parallel between a DCpositive terminal 314 and a DC negative terminal 316 that areelectrically connected to the positive and negative terminals of thebattery 136 respectively. The upper and lower arms series circuit 150 iscalled an arm and provided with the upper arm switching powersemiconductor device 328, the diode 156, the lower arm switching powersemiconductor device 330, and the diode 166.

In the present embodiment, the switching power semiconductor devices areillustrated by an example of the IGBTs 328 and 330. The IGBTs 328 and330 are provided with collectors 153 and 163, emitters (signal emitterterminals 155 and 165), and gate electrodes (gate electrode terminals154 and 164). As Figured, the diodes 156 and 166 are electricallyconnected between each of the collectors 153 and 163 and the emitters ofthe IGBTs 328 and 330, respectively. The diodes 156 and 166 are providedwith two electrodes, i.e., cathode and anode electrodes. The cathode andanode electrodes are electrically connected to the collectors andemitters of the IGBTs 328 and 330 respectively so that the directionfrom the emitters to the collectors of the IGBTs 328 and 330 is forwarddirection. A MOSFET (metal-oxide semiconductor field-effect transistor)may be employed for the switching power semiconductor device which makesthe diodes 156 and 166 unnecessary.

The upper and lower arms series circuits 150 are provided for threephases corresponding to each phase coil of the armature coil of themotor generator 192. Each of the three upper and lower arms seriescircuits 150 makes up either one of the U-phase, V-phase, or W-phase forthe motor generator 192 through the intermediate electrodes 169 whichconnect the emitters of the IGBTs 328 with the collectors 163 of theIGBT 330 and the AC terminals 159. The upper and lower arms seriescircuits 150 are electrically connected in parallel between each other.The collectors 153 of the IGBTs 328 of the upper arm and the emitters ofthe IGBTs 330 of the lower arm are electrically connected by DC busbarto a positive electrode of the capacitor module 500 via the positiveelectrode terminal (P terminal) 157 and to a negative electrode of thecapacitor module 500 via the negative electrode terminal (N terminal)158, respectively. The intermediate electrodes 169, that is, themidpoints of each of the arms (connection of the emitters of the IGBTs328 of the upper arm and the collectors of the IGBTs 330 of the lowerarm), are electrically connected to the phase coil which corresponds tothe armature coil of the motor generator 192 through an AC connector188.

The capacitor module 500 constitutes a smoothing circuit which reducesfluctuation in DC voltage generated by switching operation of the IGBTs328 and 330. The positive electrode and the negative electrode of thecapacitor module 500 are electrically connected to positive and negativesides of the battery 136 through a DC connector 138 respectively. Thecapacitor module 500 is thus electrically connected in parallel to thebattery 136 and the upper and lower arms series circuits 150 at bothbetween the collectors 153 of the upper arm IGBTs 328 and the positiveterminal side of the battery 136 and between the emitters of the lowerarm IGBTs 330 and the negative terminal side of the battery 136.

The control unit 170 is designed to operate the IGBTs 328 and 330 andincludes the control circuit 172 which generates a timing signal forcontrolling switching timing of the IGBTs 328 and 330 in accordance withinformation input from other control devices or sensors, and a drivecircuit 174, which generates a drive signal for switching operation ofthe IGBTs 328 and 330 in accordance with the timing signal output fromthe control circuit 172.

The control circuit 172 is provided with a microcomputer forcomputational processing of the switching timing of the IGBTs 328 and330. The microcomputer is provided with input information including atarget torque required for the motor generator 192, a current valuesupplied from the upper and lower arms series circuits 150 to thearmature coil of the motor generator 192, and a magnetic pole positionof the rotor of the motor generator 192. The target torque is set inaccordance with a command signal output from a superordinate controldevice not figured herein. The current value is detected in accordancewith a detection signal output from a current sensor 180. The magneticpole position is detected based on a detection signal output from arotating magnetic pole sensor (not Figured herein) provided in the motorgenerator 192. In the present embodiment, description will be given withan example of detection of three-phase current value. Two-phase currentvalue, however, may instead be detected.

The microcomputer in the control circuit 172 calculates a currentcommand value of d- and q-axis of the motor generator 192 in accordancewith the target torque, calculates a voltage command value of the d- andq-axis in accordance with the difference between the calculated currentcommand value of the d- and q-axis and a detected current value of thed- and q-axis, and converts the calculated voltage command value of theB- and q-axis into a voltage command value for U-phase, V-phase, andW-phase in accordance with the detected magnetic pole position. Themicrocomputer generates a pulse modulated wave according to comparisonof a fundamental wave (sine wave) based on the voltage command value forU-phase, V-phase, and W-phase with a carrier wave (triangle wave), andoutputs the generated modulated wave to the gate drive circuit 174 as apulse-width modulation (PWM) signal.

When the lower arm is driven, the gate drive circuit 174 amplifies andoutputs the PWM signal as a drive signal to the gate electrodes of theIGBTs 330 of the corresponding lower arm. When the upper arm is driven,the gate drive circuit 174 shifts from a reference potential level ofthe PWM signal to a reference potential level of the upper arm,amplifies and outputs the amplified PWM signal as a drive signal to thegate electrodes of the IGBTs 328 of the corresponding upper arm. Each ofthe IGBTs 328 and 330 performs switching operation in response to theinput drive signals.

The control unit 170 detects abnormality (overcurrent, overvoltage, overtemperature, etc.) for protecting the upper and lower arms seriescircuits 150. Consequently, sensing information is input to the controlunit 170. For example, information on electric current which flows tothe emitters of each of the IGBTs 328 and 330 is input through thesignal emitter terminals 155 and 165 of each arm to a correspondingdrive unit (IC). Each drive unit (IC) thus detects overcurrent, stopsswitching operation of the corresponding IGBTs 328 and 330 in the caseovercurrent is detected, and protects the corresponding IGBTs 328 and330 from overcurrent. Temperature information of the upper and lowerarms series circuits 150 is input from a temperature sensor (not Figuredherein) provided in the upper and lower arms series circuits 150 to themicrocomputer. Voltage information of positive side of DC of the upperand lower arms series circuits 150 is input to the microcomputer. Themicrocomputer detects over temperature and overvoltage based on thoseinformation, stops all switching operations of the IGBTs 328 and 330 inthe case over temperature or overvoltage is detected, and protects theupper and lower arms series circuits 150 and therefore the semiconductormodule which includes the circuits 150 from over temperature orovervoltage.

In FIG. 2, the upper and lower arms series circuits 150 are seriescircuits which include the IGBTs 328 of the upper arm, the diodes 156 ofthe upper arm, the IGBTs 330 of the lower arm, and the diodes 166 of thelower arm, wherein the IGBTs 328 and 330 are the switching semiconductordevices. Conduction operation and interrupting operation of the IGBTs328 and 330 of the upper and lower arms of the inverter circuit 144alternate constantly. Electric current through the stator coil of themotor generator 192 at the alternation flows through a circuit includesthe diodes 156 and 166.

As illustrated, the upper and lower arms series circuit 150 is providedwith the positive terminal (P terminal) 157, the negative terminal (Nterminal) 158, the AC terminals 159 from the intermediate electrode 169of the upper and lower arms, the signal emitter terminal 155 of theupper arm, the gate electrodes terminal 154 of the upper arm, the signalemitter terminal 165 of the lower arm, and the gate electrodes terminal164 of the lower arm. The power inverter 200 is provided with the DCconnector 138 on its input side and the AC connector 188 on its outputside, and is connected to each of the battery 136 and the motorgenerator 192 via each of the connectors 138 and 188. A power inverterwith circuit configuration in which two of the upper and lower armsseries circuits are connected in parallel to each phase may be employedfor a circuit that generates outputs of each phase of the three-phase ACwhich is output to the motor generator.

The entire configuration of the power inverter 200 shown in FIGS. 1 and2 will be hereinafter described with reference to FIGS. 3 to 7. A samereference number is given to the same component among FIGS. 1 to 7.Description for a component already described will be omitted. FIG. 3 isan external perspective view of an entire configuration of the powerinverter 200. FIG. 4 is an exploded perspective view of the entireconfiguration of the power inverter 200 in accordance with the presentembodiment. FIGS. 5A to 5C are the illustrations of the chassis which isa housing of the power inverter shown in FIGS. 3 and 4, and the coolantpassage provided in the chassis. FIG. 6 is a bottom view of the chassisin which the coolant passage is seen from the bottom. FIG. 7 is across-sectional view of the power inverter 200, which showscross-sectional surface of A-A in FIG. 6 seen from the top of the FIG.6.

In FIGS. 3 to 7, each component is numbered as follows: power inverter200; upper cover 10; metal board 11; chassis 12; coolant inlet 13;coolant outlet 14; cover 420; lower cover 16; AC terminal case 17; ACterminal 18; coolant passage 19; control circuit board 20 which holdsthe control circuit 172 shown in FIG. 2; connector 21 for connectionwith outside; and gate drive circuit board 22 which holds the gate drivecircuit 174 shown in FIG. 2; interboard connector 23 for electricalconnection between the control circuit 172 on the control circuit board20 and the signal line 176 shown in FIG. 2 (the signal line 176 is notFigured in FIGS. 3 to 7); power module 300 (semiconductor module unit),each of which has built-in inverter circuit 144 shown in FIG. 2; powermodule case 302; metal board 304; AC connector 188; DC positive terminal314; DC negative terminal 316; casting slots 49; capacitor module 500;capacitor case 502; positive capacitor terminal 504; negative capacitorterminal 506; and, capacitor cells 514, respectively.

The power inverter 200 in accordance with the present embodiment isroughly provided with the power module (semiconductor module unit) 300that converts between DC electric power and AC electric power, thecapacitor module 500 for voltage smoothing of DC power, and the coolantpassage 19 for cooling, for example, the power module 300. As shown inFIG. 3, the external of the power inverter 200 in accordance with thepresent embodiment includes the chassis 12 with substantiallyrectangular top or bottom surface, the coolant inlet 13 and the coolantoutlet 14 provided on one of the short sides of the chassis 12, theupper cover 10 for covering an upper opening of the chassis 12, and thelower cover 16 for covering a lower opening of the chassis 12. Two ACterminal cases 17 for connection to the motor generator 192 or 194 aremounted on one of the long sides of the power inverter 200. Thesubstantially rectangular top or bottom surface of the chassis 12realizes easier mounting on vehicles and higher productivity. It is tobe noted that a connector 21 which is shown in FIG. 4 is omitted in FIG.3 to show the rectangular shape of the chassis 12.

As shown in FIG. 4, the coolant passage 19 is provided in the chassis12. Openings 400 and 402 are formed along the flow of the coolant overthe coolant passage 19. Two power modules 300 are fixed over the coolantpassage 19 so that each of the openings 400 and 402 is covered with thepower module 300. Each of the power module 300 is provided with thecooling fin 305 that protrudes into the flow of the coolant through theopenings 400 and 402 of the coolant passage 19.

Openings 404 are formed under the coolant passage for easier aluminumcasting. The openings 404 are covered with a cover 420. The inverterdevice 43 for auxiliaries is provided beneath the coolant passage 19.The inverter device 43 for auxiliaries is provided with a built-incircuit similar to the inverter circuit 144 shown in FIG. 2 and a powermodule provided with built-in power semiconductor device which makes upthe inverter circuit 144. The inverter device 43 for auxiliaries isfixed beneath the coolant passage 19, with a cooling metal surface ofthe built-in power module facing the bottom surface of the coolantpassage 19.

The lower cover 16 for heat dissipation is provided under the coolantpassage 19 and provided with the capacitor module 500, with the coolingsurface of a metal case of the capacitor module 500 facing and fixed onthe surface of the lower cover 16. This configuration realizes efficientcooling using top and bottom surfaces of the coolant passage 19,resulting in miniaturization of the entire power inverter.

The flow of the coolant in the coolant passage 19 through the inlet 13and the outlet 14 cools the cooling fin 305 included in the two parallelpower modules 300 and thus cools the two power modules 300 overall. Atthe same time, the inverter device 43 for auxiliaries, which is providedbeneath the coolant passage 19, is cooled.

The lower cover 16, provided under the chassis 12, is cooled as thechassis 12 provided with the coolant passage 19 is cooled. The heat ofthe capacitor module 500 is thus conducted to the coolant via the lowercover and the chassis 12, resulting in cooling of the capacitor module500.

In the present embodiment, in the chassis 12, the DC positive busbars314 and the DC negative busbars 316 of the power module 300 aredirectly, electrically, and mechanically connected to the positiveterminals 504 and the negative terminals 506 of the capacitor module 500respectively. A through-hole 406 is formed for this connection.

The control circuit board 20 and the gate drive circuit board 22 areprovided over the power module 300. The gate drive circuit 174 shown inFIG. 2 is mounted on the gate drive circuit board 22. The controlcircuit 172 with CPU shown in FIG. 2 is mounted on the control circuitboard 20. The metal board 11 is placed between the gate drive circuitboard 22 and the control circuit board 20 as an electromagnetic shieldfor circuits mounted on the both boards 22 and 20 for cooling the bothboards 22 and 20 by transferring heat generated by the both boards 22and 20. Efficient cooling with small space and miniaturization of theoverall power inverter are achieved by placing the coolant passage 19 inthe center of the chassis 12, the power module 300 for driving a vehicleon one side of the coolant passage 19, and the inverter device 43 forauxiliaries on the other side. Main mechanism of the coolant passage 19is formed with aluminum casting together with the chassis 12 for bettercooling effect and mechanical strength of the coolant passage 19.Forming with the aluminum casting realizes integral structure of thechassis 12 and the coolant passage 19, resulting in better heat transferand cooling effect.

The gate drive circuit board 22 is provided with the interboardconnector 23 for connection with the circuits on the control circuitboard 20 through the metal board 11. The control circuit board 20 isprovided with the connector 21 for electrical connection with outside.The connector 21 enables signal transmission with the battery 136 whichis, for example, a lithium battery module mounted on a vehicle. Signalsindicating a battery status or a charging status of the lithium batteryare sent from the lithium battery module. The interboard connector 23 isprovided for signal transference with the control circuit 172 mounted onthe control circuit board 20. Switch timing signal for the invertercircuit is transmitted from the control circuit board 20 to the gatedrive circuit board 22 through the signal line 176 and the interboardconnector 23. Gate drive signal is generated at the gate drive circuitboard and applied on each of the gate electrodes of the power module.

The openings are formed at an upper part and a lower part of the chassis12. These openings are covered with the upper cover 10 and the lowercover 16 fixed to the chassis 12, for example, with screws. The coolantpassage 19 is provided in the center of the chassis 12. The power module300 and the cover 420 are fixed to the coolant passage 19. The coolantpassage 19 is thus formed and tested for water leak. After passing thewater leak test, boards and the capacitor module 500 are fixed throughthe upper and lower openings of the chassis 12. The configuration withthe coolant passage 19 provided in the center and the upper and loweropenings of the chassis 12 through which necessary parts are installedand fixed leads to better productivity. The water leak test after thecompletion of the coolant passage 19 realizes higher productivity andreliability.

FIGS. 5A to 5C show an aluminum cast of the chassis 12 which includesthe coolant passage 19. FIG. 5A is a perspective view of chassis 12.FIG. 5B is a top view of the chassis 12 seen from an arrow B in FIG. 5A.FIG. 5C is a bottom view of the chassis 12 seen from an arrow C in FIG.5A. As shown in FIG. 5A, the chassis 12 and the coolant passage 19formed in the chassis 12 are integrally casted. The upper surface or thelower surface of the chassis 12 is substantially rectangular. An inlet401 for taking in the coolant is provided on one of the short sides ofthe chassis. An outlet 403 for coolant is provided on the same side.

After flowing into the coolant passage 19 through the inlet 401, thecoolant flows along one of the long side of the rectangle as shown by anarrow 418, turns at just before the other one of the short sides of therectangle as shown by an arrow 421, flows along the other of the longsides of the rectangle as shown by an arrow 422, and flows out from theoutlet 403. One pair of the openings 400 and 402 is provided in eachdirection of the coolant passage 19. The power modules 300, shown belowin FIG. 13, are fixed to each of the openings. The cooling fin 305 forcooling each of the power modules 300 protrudes into the flow of thecoolant through each of the openings. The power modules 300 are fixed inparallel along the flow, that is, the long side of the chassis 12. Asupport part 410 is thus integrally formed with the chassis so that eachof the power modules 300 may fully cover the openings of the coolantpassage 19. The support part 410 is formed in a substantial center ofthe chassis 12. One of the power modules 300 is fixed to the supportpart 410 on the side where the inlet and outlet of the coolant exist,while the other power module 300 is fixed to the support part 410 on theother side where the coolant turns. Threaded holes 412 shown in FIG. 5Bare used for fixing the power module 300 on the inlet and outlet side tothe coolant passage 19. The opening 400 is thus sealed. Threaded holes414 are used for fixing the power module 300 on the other side to thecoolant passage 19. The opening 402 is thus sealed.

The power module 300 on the inlet and outlet side is to be cooled byboth cold coolant from the inlet 401 and warmed coolant which flows nearthe outlet. On the other hand, the power module 300 on the other side isto be cooled by coolant with more moderate temperatures. As a result,the configuration of the coolant passage and the two power modules 300has an advantage in balanced cooling efficiency of the two power modules300.

The support part 410 is necessary for fixing the power modules 300,sealing the openings 400 and 402, and strengthening the chassis 12. Apartition wall 408 is provided for separation of the back and forth flowof coolant in the coolant passage 19. The partition wall 408 isintegrally formed together with the support part 410 and alsostrengthens the chassis 12. The partition wall 408 transfers the heatbetween the back and forth passages, and equalizes the coolanttemperature flowing through them. Large difference between the back andforth coolant temperature diminishes the cooling efficiency. Since thepartition wall 408 is integrally formed together with the support part410, the difference in the coolant temperature is reduced.

FIG. 5C shows the reverse side of the coolant passage 19. The openings404 are formed on the reverse side at an area corresponding to theposition where the support part 410 exists. The openings 404 improveyield of the integral structure of the support part 410 with the chassis12. The openings 404 remove double structure of the support part 410 andthe bottom of the coolant passage 19, make the casting easier, andimprove productivity.

The through-hole 406 is formed between the side of the coolant passage19 and the long side of the rectangle chassis to pass through upper andlower sides of the passage. Electrical components on the both sides ofthe coolant passage 19 are electrically connected to each other throughthe through-hole 406.

The chassis structure shown in FIGS. 5A to 5C is suitable for casting,particularly aluminum die casting, because of the integral structure ofthe coolant passage 19 with the chassis 12. Since the part where thecoolant turns shown by the arrow 421 is a part of the opening 402,integral casting of the turn part of the passage is made possible. Byfixing the power module 300 to the opening 402, a bent passage isrealized. Moreover, miniaturization is realized by utilizing the turnpart of the passage for cooling. Inner walls defining the coolantpassage 19 and the sides of the partition wall 408 are substantiallyvertical to the surface at which the openings are formed. Thisconfiguration enables the passage to be formed by the power modules 300fixed to the openings 400 and 402 on the front surface and the cover 420fixed to the bottom surface. At this point of the production, the waterleak of the passage is inspected before the components are mounted. Thisresults in removal of defectives in early stage of the production andimprovement of the productivity.

The power modules 300 are fixed on the upper openings 400 and 402 andthe cover 420 is fixed on the lower openings 404 of the coolant passage19, as shown in FIG. 6. The AC electric power lines 186 and the ACconnectors 188 protrude from the chassis 12 on one of the long sides ofthe rectangle of the chassis 12. The cross-sectional view in FIG. 7shows the AC terminal case 17 mounted on the AC connector 188 side ofthe power inverter 200 for connecting the AC terminals of the motorgenerator 192 and 194 with the AC connectors 188.

FIG. 6 shows the through-hole 406 formed inside the other long side ofthe rectangle of the chassis 12 and the DC positive terminals 314 andthe DC negative terminals 316 of the power module 300 seen through thethrough-hole 406. The inverter device 43 for auxiliaries herein shown indashed line is yet to be mounted. The coolant inlet 13 and the coolantoutlet 14 are fixed with screws. After passing the water leak test whichcan be conducted in this stage of the production shown in FIG. 6, theinverter device 43 for auxiliaries and the capacitor module 500 aremounted.

FIG. 7 is the cross-sectional view of the power inverter 200 withnecessary components and wirings. The basic structure is described abovewith reference to the FIGS. 3 to 6. In FIG. 7, unlike FIGS. 3 to 6, theAC terminal case 17 for connection between the terminal of motorgenerator 192 and the AC connector 188 is mounted on the AC connector188 side of the power inverter 200.

As shown in FIG. 7, the two passages of the coolant passage 19integrally formed with the chassis 12 are provided at a substantialcenter of the cross-section of the chassis 12 in a vertical direction.The power modules 300 are placed in the opening formed at the upper sideof the coolant passage 19. A left passage in FIG. 7 is the forth coolantpassage 19 and a right passage is the back coolant passage 19. Asdescribed above, each of the back and forth coolant passage 19 isprovided with the openings. The openings are covered with the metalboards 304 for cooling the power modules 300. The cooling fins 305provided on the metal boards 304 protrude through the openings into theflow of the coolant. The inverter device 43 for auxiliaries is fixed onthe lower side of the coolant passage 19.

As shown on the left side of FIG. 7, the AC electric power line 186 withcross-section in rectangular parallelepiped shape, or busbar shape,leading out of inside the power module 300, forms the AC connector 188.On the right side of FIG. 7, the DC positive and negative terminals 314and 316 with cross-section in rectangular parallelepiped shape, orbusbar shape are provided respectively. The through-hole 406 is formedon the right side of the coolant passage 19 in the chassis 12. The DCpositive and negative terminals 314 and 316 are directly, electrically,and mechanically connected to the positive and negative terminals of thecapacitor leading out of the capacitor module 500. The coolant passage19 is formed in the substantial center of the chassis 12 with back andforth passages along the long side of the rectangle. Since the ACconnector 188 and the DC positive and negative terminals 314 and 316 areplaced substantially vertical to the flow of the coolant, electricwiring is orderly configured, resulting in miniaturization of the powerinverter 200. The DC positive and negative busbars 315 and 317 and theAC electric power line 186 of the power module 300 protrude from thepower module 300 and make up the connecting terminal. This results in asimple structure. Since other connection conductor is not used,miniaturization is realized. This structure improves both productivityand reliability. The through-hole 406 through which the DC positive andnegative terminals 314 and 316 of the power module 300 and negative andpositive terminals 504 and 506 of the capacitor module 500 connect witheach other is separated from the coolant passage 19 by a frame in thechassis 12. This configuration improves reliability.

The aluminum lower cover 16 with high heat conduction is provided forthe lower openings of the chassis 12. A metal capacitor case 502 for thecapacitor module 500 is fixed to the lower cover 16. The lower cover 16is cooled by the coolant flowing through the coolant passage 19 throughthe chassis 12. Heat generated inside the capacitor module 500 is cooledthrough the lower cover 16.

The power modules 300 with high heating value are fixed on one of thesides of the coolant passage 19. The fins 305 of the power modules 300protrude into the passage through the openings of the coolant passage 19for more efficient cooling. The inverter device 43 for auxiliaries withnext higher heat radiation is cooled on the other side of the coolantpassage 19. The capacitor module 500 with next higher heating value iscooled through the chassis 12 and the lower cover 16. With the coolingstructure in accordance with the heat radiation value, coolingefficiency and reliability are improved, at the same time, the powerinverter 200 is miniaturized more.

Since the inverter device 43 for auxiliaries is fixed on the side of thecoolant passage 19 facing the capacitor module 500 of, the capacitormodule 500 is used as a smoothing capacitor for the inverter device 43for auxiliaries. This configuration shortens the wiring, resulting inreducing inductance.

The gate drive circuit board 22 which holds the gate drive circuit 174shown in FIG. 2 is placed above the power modules 300. The controlcircuit board 20 on which the connector 21 is mounted is placed abovethe gate drive circuit board 22 through the metal board 11, whichreleases heat and acts as electromagnetic shield. The control circuitboard 20 is provided with the control circuit 172 shown in FIG. 2. Byfixing the upper cover 10 to the chassis 12, the power inverter 200 inaccordance with the present embodiment is assembled.

Since the gate drive circuit board 22 is placed between the controlcircuit board 20 and the power module 300, instructions for operationtiming of the inverter circuit are sent from the control circuit board20 to the gate drive circuit board 22; gate signals are generated in thegate drive circuit board 22 in response and applied on each gate of thepower modules 300. Configuration of the control circuit board 20 and thegate drive circuit board 22 according to the electrical connection makesthe electrical wiring simple and the power inverter 200 small.

FIG. 8 shows the cooling mechanism. Fixing the power modules 300 on oneof the sides of the coolant passage 19 and the inverter device 43 forauxiliaries on the other side enables both the power modules 300 and theinverter device 43 for auxiliaries to be cooled at the same time by thecoolant passage 19. Better cooling effect is realized because thecooling fins of the power modules 300 contact with the coolant flowingin the coolant passage 19. The coolant passage 19 cooles the chassis 12on which the lower cover 16 and the metal board 11 are fixed. The metalcase of the capacitor module 500 is fixed on the lower cover 16. Thecapacitor module 500 is thus cooled through the lower cover 16 and thechassis 12. Likewise, the control circuit board 20 and the gate drivecircuit board 22 are cooled through the metal board 11. Configurationwith the coolant passage 19 at the center, the metal board 11 on oneside, and the lower cover 16 on the other side realizes efficientcooling of the components for the power inverter 200 in accordance withthe heating value. The components are orderly placed in the powerinverter 200, resulting in miniaturization.

The coolant passage 19 with the power modules 300 mounted is tested forwater leak. After passing the test, necessary components are fixedthrough the upper and lower openings of the chassis 12. This improvesproductivity.

Features of the power inverter 200 in accordance with the embodiment ofthe present invention will be further described. In the overalllaminated structure and cooling structure of the power inverter inaccordance with the present embodiment, the power modules 300, which aremajor heating elements, are directly cooled by the coolant flowing inthe coolant passage 19. The coolant passage 19 is sandwiched between thecapacitor module 500, which is another heating element, and the powermodules 300. This sandwiched laminated structure realizes thinness andsmallness.

Cooling elements for the power inverter 200 primarily include thecoolant passage 19. Other cooling elements include the metal board 11,which functions as the electromagnetic shield. The metal board 11transfers the heat from the control circuit board 20 and the gate drivecircuit board 22 to the chassis 12, and is cooled by the coolant of thecoolant passage 19. The lower cover 16, made of highly heat-conductivematerial, also transfers the heat from the capacitor module 500 to thechassis 12, and is cooled by the coolant of the coolant passage 19. Onthe side of the lower cover 16 of the coolant passage 19 exists, theinverter device 43 for auxiliaries with relatively small capacity may beplaced for the on-vehicle air conditioner, the oil pump, and otherpumps. The heat from the inverter device 43 for auxiliaries is cooled bythe coolant of the coolant passage 19 through the frame in the chassis12.

In the power inverter in accordance with the present embodiment, thecooling element has the three-layer laminated structure: the metal board11, the coolant passage 19 of a cooling section 9, and the lower cover16. These cooling elements are hierarchically placed adjacent to eachheating element (the power modules 300, the circuit boards 20 and 22,and the capacitor module 500). The coolant passage 19, which is a majorcooling element, exists in the center of the hierarchical structure. Themetal board 11 and the lower cover 16 transfer the heat to the coolantof the coolant passage 19 through the chassis 12. The three coolingelements (the coolant passage 19, the metal board 11, and the lowercover 16) are contained in the chassis 12 and improve in coolingperformance, reducing thickness, and miniaturization.

The external structure of each side of the power inverter in accordancewith the present embodiment will be hereinafter described with referenceto FIGS. 9 to 11. FIG. 9 is the left side view of the power invertershown in FIG. 3 in accordance with the present embodiment. FIG. 10 isthe right side view of the power inverter shown in FIG. 3 in accordancewith the present embodiment. FIG. 11 is the rear view of the powerinverter shown in FIG. 3 in accordance with the present embodiment.

As shown in FIG. 9, the inlet 13 and the outlet of the coolant arejuxtaposed to each other in the center of the chassis 12 in a verticaldirection. The power modules 300 are cooled through the metal board 304by circulation of the coolant through the inlet 13 and the outlet 14.The metal board 11 for the electromagnetic shield is placed at the topof the chassis 12. The upper cover 10 is fixed on the metal board 11,while the lower cover 16 is fixed on the bottom of the chassis 12. Thepower inverter in accordance with the present embodiment is thusintegrally structured. Highly heat-conductive material, for examplealuminum, is employed for the chassis 12 so that the cooling effectthrough the coolant passage is efficiently conducted to the capacitormodule 500 via the chassis 12.

Placing the inlet 13 and the outlet 14 juxtaposed to each other on theshort side of the rectangular chassis 12 results in lengthening theinside cooling passage and in easier pipework operation when the powerinverter 200 is mounted on a vehicle.

FIG. 10 shows the opposite side of the side shown in FIG. 9. Theconnector 21 of the control circuit board 20 shown in FIG. 4 is providedon the upper cover 10. The connector 21 is a connecting terminal for thecontrol unit 170 shown in FIG. 2 to transfer signals with outside. Thechassis 12 is provided with the DC positive connecting terminal 510 andthe DC negative connecting terminal 512 to be connected to the battery.These connecting terminals 510 and 512 correspond to the DC connector138 shown in FIG. 2. The AC electric power line 186 protrudes from thechassis 12 and makes up the AC connector 188 at the end of the line 186.

Since the connecting terminals to the battery and the connector 21 forsignal line are provided on the opposite side of the side where theinlet 13 and the outlet 14 of the coolant are provided, reliability isimproved. Also, workability for mounting the power inverter 200 on avehicle is improved.

FIG. 11 is the rear view of the power inverter shown in FIG. 3, showingthe AC connectors 188, which make up AC connecting terminals to themotor, provided on the rear surface. The connector 21 from the controlcircuit board 20 and the coolant inlet 13 protrude left and right,respectively in FIG. 11. The casting slots 49 for casting the chassismaterial are formed on the chassis 12. FIG. 11 shows an example ofjuxtaposed two power modules (semiconductor modules) 300 provided withthe AC electric power line 186 of U-phase, V-phase, and W-phase,including three of the upper and lower arms series circuits shown inFIG. 2.

As seen from the FIG. 11, supply and discharge of the coolant, transferof DC electric power, and transfer of AC electric power are operated ondifferent side of the chassis 12 respectively. This contributes toimprovement in workability and reliability.

The power modules 300 of the power inverter in accordance with thepresent embodiment will be hereinafter detailed with reference to FIGS.12 to 14 and 21. FIGS. 12-14, and 21 show only one of the power modules300 to facilitate explanation. FIG. 12 is the top perspective view ofthe power module 300 which relates to the present embodiment. FIG. 13 isthe bottom perspective view of the power module 300 which relates to thepresent embodiment. FIG. 14 is the cross-sectional view of the powermodule which relates to the present embodiment. FIG. 21 is the plainview of the power module which relates to the present embodiment.

In FIGS. 12 to 14 and 21, components are numbered as follows: powermodule (semiconductor module) 300; power module case 302; metal board304; cooling fin 305; AC electric power line with substantiallyrectangular cross-section 186; DC positive terminal 314; DC negativeterminal 316; thin insulation member 318; IGBT control terminal 154/155for the upper arm of the power module 300; IGBT control terminal 164/165for the lower arm of the power module 300; resin or silicone gel forchip protection 322; pin 324 for holding the AC electric power linewhich acts as AC busbar; IGBT for the upper arm 328; IGBT for the lowerarm 330; diode 156/166; insulation substrate board 334; and, conductor337, respectively.

The power module 300 is roughly provided with the semiconductor moduleincluding wiring in the power module case 302 made of resin material,for example; the metal board 304 made of metallic material such as Cu,Al, or AlSiC; and, connecting terminals with outside. The power module300 is provided with connecting terminals with outside such as the ACconnector 188 of U-phase, V-phase, and W-phase for connecting to themotor, the DC positive terminals 314 and the DC negative terminals 316to be connected to the capacitor module 500. The semiconductor module isprovided with the IGBTs 328 and 330 of the upper and lower arms on theinsulation substrate board 334 and the diodes 156 and 166, and isprotected by resin or silicone gel 322. The insulation substrate board334 may be either a ceramic substrate or a thinner insulation sheet. Themetal board 304 is provided with the fin 305 on the back side of theinsulation substrate board 334 to be immersed into the coolant in thecoolant passage for efficient cooling.

The DC terminals 314 and 316, which connect with the capacitor module500, are soldered or ultrasonically-bonded at points to be connected(refer to FIG. 14) in the center of the board 334 according to FIG. 21.The DC terminals 314 and 316 provided with the thin insulation member318 lying between the terminals 314 and 316 for insulation, are broughtto the right edge of the power module 300 with the DC terminal 314 overthe insulation member 318 and the DC terminal 316. Both the DC terminals314 and 316, which are busbars, and the insulation member 318 are thentwisted. Lastly, as shown in FIG. 21, the terminals that connect to theterminals of the capacitor are aligned.

As shown in FIGS. 12 to 14 and 21, one side of the metal board 304 isprovided with the resin power module case 302 with the built-in IGBTsand diodes that constitute the inverter circuit. The fin 305 is brazedon the other side of the metal board 304 as shown in FIG. 13. Theinsulation substrate board 334 fixed on the one side of the metal board304 as shown in FIGS. 14 and 21. The thin conductors 337 are attached tothe insulation substrate board 334; and chips of the upper arm IGBTs328, the upper arm diodes 156, the lower arm IGBTs 330, and the lowerarm diodes 166 are fixed on the conductors 337, for example, withsolder. The chips of the upper arm are fixed on the metal board 304 sideof the laminated busbars 315 and 317, in other words, on the DCterminals side as in FIG. 14. The chips of the lower arm are fixed onthe AC connector 188 side of the laminated busbars 315 and 317. DCelectricity is thus supplied from the substantial center for reducinginductance as hereinafter described.

The fin 305 is brazed at positions corresponding to the chips of theboth upper and lower arms across the metal board 304 (FIGS. 13 and 14).The fin 305 protrudes into the coolant passage 19 through the openingsof the passage. Metal surface around the fin 305 of the metal board 304is used for covering the openings provided over the coolant passage 19.

As shown in FIG. 14, the AC electric power line 186 is connected to theAC terminals 159 (refer to FIG. 2) which are connection points of theupper and lower arms, protrudes from the power module 300, and makes upthe AC connector 188 at the end of the line 186. FIGS. 12 and 13 showthe AC electric power lines 186 corresponding to U-phase, V-phase, andW-phase that protrude from the power module case 302 and make up the ACconnector 188.

The AC electric power line 186 fixed to the power module 300 isdescribed with reference to FIG. 14. The AC electric power line 186 withsubstantially rectangular parallelepiped cross-section is fixed to anappropriate part of the insulation substrate board 334 at the right end(FIG. 14) of the line 186 with, for example, solder, and is connected tothe connecting terminals (not figured herein) from the motor generator192 at the AC connector 188, which is the left end of the line 186. Theleft end side of the AC electric power line 186 is sensitive to thevibration of in-vehicle motor. The AC electric power line 186 is therigid conductor with substantially rectangular parallelepipedcross-section so as to transfer a high current. The vibration of themotor transmitted to connecting parts of the insulation substrate board334 via the AC electric power lines 186 may lead to loose connection ofthe connecting parts. In the present embodiment, therefore, as shown inFIG. 21, the pins 324 are used for holding the AC electric power lines186 between the connecting parts and the AC connector 188, so that thevibration of the motor may not be transmitted directly to the connectingparts of the insulation substrate board 334.

The pins 324 are integrally or semi-integrally formed with the powermodule case 302. The AC electric power line 186 is positioned byinserting the pins 324 for positioning. Otherwise, the pins 324 may beinserted into holes of the power module case 302 for positioning withthe pins 324 and the AC electric power lines 186 (bent busbar)integrally or semi-integrally structured. In other words, as long as thepins 324 absorb stress such as the vibration of the motor, withoutleaving any outside stress to the connecting parts between the ACelectric power lines 186 and the insulation substrate board 334, themeans is not limited to pins. FIG. 21 shows an example with the two pinsprovided for each phase of the AC electric power line 186. Pins may becylindrical or cross-shaped.

As seen from FIGS. 6 and 11, the AC electric power lines 186 protrudefrom the chassis 12 and are flexibly connectable to the connectingterminals of the motor. Thus, intermediate members for connectionbetween the AC connector 188 and the AC output terminals of the powermodule 300 are not necessary. Since the AC electric power lines 186protrude from the chassis, it is easier to connect with the connectingterminals of the motor with smaller number of components andconnections. This configuration improves workability and reliability,compared to conventional configuration where the terminals of the ACelectric power lines 186 are fixed to and contained in the case of thepower module 300. Thus, a synergistic effect, the removal of the effectof outside stress or vibration on the insulation substrate board 334 andthe easy connection with the connecting terminals of the motor, isgenerated because of the configuration with the protruding AC electricpower line 186 and the pins 324.

The insulation substrate board 334 is formed with Cu or Al film on bothsides of a ceramic plate. FIG. 14 shows an example with the insulationsubstrate board 334 on which the metal board 304 (Cu, Al, or AlSiC) withfins or pins is fixed on the underside of the board 334. The IGBTs 328and 330 and the diodes 156 and 166 are soldered on the topside of theboard 334, and the DC terminals 314 and 316 ultrasonically-bonded bothon the topside of the board 334. The control terminals 154, 155, 164,and 165 of the power module illustrated in FIG. 21 are the gateelectrodes terminals 154 and 164 and the emitter terminals 155 and 165of the upper and lower arms shown in FIG. 2. Signal for controlling theswitching operation of the IGBTs are applied to these terminals.

Further description for the configuration of the upper and lower armsseries circuits in the power module 300 (FIG. 21) is given below. Asseen from the cross-sectional view of the power module 300, theinsulation substrate board 334 made of ceramic with Cu film on bothsides is soldered on the metal board 304 provided with the fin 305 (FIG.14). The metal board 304 itself and the fin 305 have high heatconductivity and heat release function. Heating elements such as thediodes 156 and 166 and the IGBTs 328 and 330 are soldered on the upperCu film of the metal board 304.

FIGS. 20A to 20C show the schematic diagrams of the actual configurationof the upper and lower arms series circuit and its functions and effectson the ceramic insulation substrate board 334 mounted on the metal board304. Inductance of the power module is reduced as described below. TheDC positive terminal 314, which makes up the connecting terminal of thepower module 300, is integrally formed with the positive busbar 315,extends over the upper arm, and solders a junction 339 for connectingwith a conductor 329. Likewise, the DC negative terminal 316 isintegrally formed with the negative busbar 317, extends over the upperarm, and solders a junction 341 for connecting with a conductor 337 asshown in FIG. 20A.

In accordance with the present embodiment, the junctions 339 and 341 aredisposed close to each other in the substantial center and left of theinsulation substrate board 334 (refer to FIG. 20A). The DC terminals 314and 316 and the junctions 339 and 341 are connected by the positivebusbar 315 and the negative busbar 317 respectively, which are laminatedwith the thin insulation 318. Current directions of the positive busbar315 and the negative busbar 317 are opposite to each other (refer toarrows of current flow 338). The IGBTs 328 and 330 and the diodes 156and 166 (FIG. 20) are connected in parallel respectively to form twoarms, and increase electric current flowing through the upper and lowerarms. By arranging the junctions 339 and 341 adjacent to each other,recovery current that flows through the upper and lower arms is allowedto flow in a circle from the junction 339 to the junction 341. Thecurrent flowing in the circle induces eddy current on the metal board304 and results in reduction in inductance to the recovery current.

Reduction in inductance inside the power module 300 will be detailedbelow with reference to FIGS. 16 to 21. Relationship between recoverycurrent and spike voltage, heat generation, and effect of reduction ininductance will be described with reference to FIGS. 16 to 20. Theabove-described inverter circuit 144 (FIG. 2) is provided with the upperand lower arms series circuits 150 corresponding to each of threephases. In normal operations, when either the IGBT 328 of the upper armor the IGBT 330 of the lower arm of the upper and lower arms seriescircuit 150 conducts electricity, the other IGBT interrupts electricity.In short, the upper and lower IGBTs do not conduct electricitysimultaneously. So, current that short-circuits through the upper andlower IGBTs does not exist. However, current that short-circuits throughthe upper and lower arms series circuit 150 generates in an invertercircuit which includes the IGBT or the MOSFET. This current is a currentarisen from recovery current, and also arisen from the diodes 156 and166 connected in parallel to the IGBTs. In an inverter circuit includingthe MOSFETs, diodes equal to the diodes 156 and 166 are provided insideeach of the MOSFETs, which ends up in the same phenomena. A circuit thatincludes the IGBT is described as a representative.

An example of the recovery current will be described with reference toFIGS. 16A and 17. FIG. 16A shows one IGBT 330 of a plurality of theIGBTs. Connector of the IGBT 330 is connected to the positive terminalof the battery 136 via the reversely-connected diode 156 and the motorgenerator 192. The emitter of the IGBT 330 for lower arm is connected tothe negative terminal of the battery 136. FIG. 16A shows that a returncurrent of the stator of the motor generator 192 flows via the diode 156with the lower arm IGBT 330 interrupted.

FIG. 16B shows that when the lower arm IGBT 330 conducts electricity, acurrent flows from the positive terminal of battery 136 to the negativeterminal of the battery 136 via a floating inductance 335, the stator ofthe motor generator 192, and the lower arm of the IGBT 330. The upperarm diode 156 is hereat reverse-biased. Since a recovery current 614flows, however, collector current of the IGBT flows with the recoverycurrent 614 in addition to a current 600 which flows through the motorgenerator 192. If stored carrier of the upper arm diode 156 flows as therecovery current 614, the stored carrier disappears; depletion layer isgenerated in the diode 156; and, the current 614 disappears. Thecollector current of the lower arm IGBT 330 includes only the current600 shown in FIG. 16C.

FIG. 17 shows a collector current 606 and a collector voltage 604 of thelower arm IGBT 330. Status shown in FIG. 16A corresponds to a leftmoststatus on a time axis of the graph in FIG. 17. When drive voltage isapplied to gate of the IGBT 330, gate current starts flowing. Thiscurrent recharges capacity both between gate and emitter and betweengate and collector. As these get recharged, gate voltage of the lowerarm IGBT 330 increases. The return current of the motor generator 192flows through the upper arm diode 156. The collector current 606 of thelower arm IGBT 330 starts flowing at t0, when the gate voltage 602exceeds a threshold level Vth1.

At that time, a superimposed current of the recovery current 614 of thediode 156 and the current 600 that flows the motor generator 192 flowsthrough the lower arm IGBT 330 as the collector current 602 of the IGBT330. The IGBT 330 conducts electricity after t1. The voltage 604 betweenthe collector and the emitter rapidly decreases. Since the current thatthe recovery current 614 is added to the current 600 that flows throughthe motor generator 192 flows through the IGBT 330, the collectorcurrent 606 has a peak current 614, which is larger than the current600. On the other hand, when the stored carrier of the diode 156disappears, the recovery current 614 disappears, and the collectorcurrent 606 of the IGBT 330 becomes the current 600 that flows throughthe motor generator 192.

From t0 to t2, the voltage 604 between the collector and the emitter ishigh. Therefore, turn-on power loss is generated and extreme heat isgenerated in the IGBT 330. Voltage is generated by changed current ofthe collector current 606, which is the sum of the current 600 and therecovery current 614, and the inductance 335. Spike voltage is generatedby the inductance 335 of the DC circuit, which flows the upper and lowerarms because the recovery current 614, in particular, flows through theupper and lower arms.

The above description is an example of the current that flows throughthe upper and lower arms. The IGBTs of the upper and lower arms do notsimultaneously conduct electricity in a control method or a controlledstate of the inverter circuit 144. However, a current that passes theupper and lower arms often flows actually.

The interruption operation of the IGBT will be described with referenceto FIGS. 18A and 19. The same numbered components are common betweenFIGS. 16A to 16C, 18A and 18B. In FIG. 18A, the lower arm IGBT 330conducts electricity. The collector current is flowing through the lowerarm IGBT 330 from the battery 136 via the floating inductance 335 andthe stator of the motor generator 192. The collector voltage of thelower arm IGBT 330 hereat is low as indicated by dashed-dotted line inFIG. 19. A line 624 shows change in the collector current.

When a gate voltage 622 of the power module 300 is reduced to below thethreshold level Vth2, the collector current 624 starts to decrease, anda voltage 626 indicated by the dashed-dotted line and applied to thecollector increases (FIG. 19). When the collector current of the lowerarm IGBT 330 starts reducing, spike voltage (L×di/dt) is generatedbecause of a reduction rate di/dt and the inductance element 335 in theDC circuit. And, a resultant vector of the collector voltage of thelower arm IGBT 330 and the spike voltage becomes a voltage generated inDC circuit, for example, between the DC positive terminal 314 and the DCnegative terminal 316. The collector voltage becomes high because of thespike voltage applied between the collector and the emitter of the IGBT330.

Reduction in the gate voltage 622 to below the threshold level Vth2results in increase in the voltage 626 (indicated by the dashed-dottedline) applied to the collector voltage of the lower arm IGBT 330, whichreaches its peak voltage 628 (FIG. 19). Next, when channel of the IGBT330 disappears, the collector current stops flowing. The current of themotor generator 192 is maintained by returning through the diode 156(FIG. 18B).

The collector current shown in FIG. 19 has a variation range Δi, whichis the collector current change at turn-off. At is period of time forthe reduction in the collector current from 10% to 90%, or time forchangeover operation. As mentioned above, when a time change rate ofcurrent Δi/Δt gets larger, the spike voltage (L×Δi/Δt) is generated bytime change of the current in the inductance 335 because the floatinginductance 335 (inductance element L) exists on the circuit of the IGBT330. Direction of a vector is not described herein. High voltage isapplied to elements and devices by the spike voltage, leading to voltagebreakdown or noise generation. Loss, or heat, is generated based onproduct of the collector current and the collector voltage of the lowerarm IGBT 330.

For reduction in the spike voltage, the time change rate Δi/Δt should bereduced, that is, change in the gate voltage should be slowed. Althoughthe time change rate of the collector current Δi/Δt and subsequent spikevoltage are reduced, a period for heat generation Δt+T and a subsequentheating value are increased. High spike voltage is thus not generatedeven if the floating inductance 335 (L) and the subsequent time changerate Δi/Δt are reduced. Therefore, it is preferable that the period forheat generation Δt+T is shortened by reduction in the time change rateΔi/Δt.

Conventionally, a heating value per unit time has been reduced byreduction in the number of operations of the IGBT of the invertercircuit 144 per unit time. In other words, frequency of PWM (pulse-widthmodulation) to control the gate of the IGBT has been decreased. However,decreasing of the frequency is not preferable in terms of controlresponse and control precision.

In accordance with the present embodiment, inductance of the DC circuitof the inverter circuit is greatly reduced. It is very easy to realize60 nanohenry or less. It is easy to realize 30 nanohenry or less.Appropriate configuration realizes 20 nanohenry or less. The time changerate Δi/Δt is increased by decreasing the inductance element. Switchingfrequency (basic frequency of PWM) of the IGBT 330 can be increased. Forexample, it is possible to increase the switching frequency by 1 kHz ormore, preferably by 10 kHz or more. It is possible to make switchingoperation time (Δt in FIG. 19: the period of time for the collectorcurrent to decrease from 90% to 10%) 1 μs or less, preferably 0.5 μs orless, or more preferably 0.2 μs or less. In the power inverter 200 withsuch characteristics, it is possible to greatly reduce the heating valuewith the spike voltage properly controlled and with high-performancecontrollability ensured. Engine coolant may be used for the coolantdepending on the heating value.

Reduction in inductance of the power module 300 will be described withreference to FIGS. 20A to 21. As above described, FIG. 21 is the topview of the power module 300. FIGS. 20A to 20C are the schematicdiagrams for effects of the reduction in inductance with the upper andlower arms series circuit 150 for one of the three phases as arepresentative. The description is applicable to the rest of the threephases. FIG. 20A shows configuration of chips of the upper and lowerarms series circuit 150 and the flow of the recovery current of thediode. FIG. 20B shows the circuit where the recovery current of thediode flows. FIG. 20C illustrates induced current generated on the metalboard 304.

The power module 300 shown in FIG. 21 is provided with the fin 305 onthe back side of the metal board 304 as shown in FIG. 14. The thininsulation 334 such as a ceramic substrate is fixed by, for example,soldering on the surface of the metal board 304. The conductors 329,331, 333, and 337 made of, for example, copper film are fixed on thesurface of the thin insulation 334. Chips of the IGBT 328 and the diode156 are electrically connected to the conductor 329 with a collectorsurface of the IGBT chip and a cathode surface of the diode chip fixedon the surface of the conductor 329. Chips of the IGBT 330 and the diode166 are electrically connected to the conductor 333 with collectorsurface of the IGBT chip and cathode surface of the diode chip fixed onthe surface of the conductor 333.

The positive busbar 315, which is provided integrally with the DCpositive terminals 314 of the power module 300, and the negative busbar317, which is provided integrally with the DC negative terminals 316 ofthe power module 300, are laminated with the insulation member. Thelaminated busbars extend to the substantial center over the part wherethe upper arm is placed. The positive busbar 315 is connected to theconductor 329 at the junction 339. The negative busbar 317 is connectedto the conductor 337 at the junction 341. In accordance with the presentembodiment, the junctions 339 and 341 are disposed adjacent to eachother in the substantial center of the conductor 329 for the upper armand the conductor 337 for the lower arm. With the junctions 339 and 341positioned closely to each other, the recovery current that flowsthrough the upper and lower arms flow in the closed circle from thejunction 339 to the junction 341. The recovery current of the diode ofthe inverter circuit 144 flowing in the circle induces the eddy currenton the metal board 304. Magnetic flux by the induced current andmagnetic flux by the recovery current cancel each other out, results inreduction in inductance related to the recovery current.

Connecting terminals that connect the upper arm with the lower arm aredenoted by terminals A and B (FIGS. 20A and 20B). The terminals A and Bare juxtaposed to each other in the substantial center and right (as anexample in accordance with the present embodiment) and connected eachother with a wire 336. The terminals A and B correspond to theintermediate electrodes 169 (FIG. 2). As in accordance with the presentembodiment, placing the junctions 339 and 341 on one side of right orleft, and the junction of the upper arm and lower arms on the other sidemakes the recovery current flow more in the circle and results in moreeffective reduction in inductance.

As illustrated, the recovery current 338 of the diode of the invertercircuit 144 flows all the way from the DC positive terminal 314 to theDC negative terminal 316 via the junction 339, either the IGBT 328 orthe diode 156 of the upper arm, the terminal A, the wire 336, theterminal B, either the IGBT 330 or the diode 166 of the lower arm, andthe junction 341. The current 338 flows in the circle which is made asclosed as possible by juxtaposition of the junctions 339 and 341. Theconductors between the DC positive terminal 314 and the junction 339 andbetween the DC negative terminal 316 and the junction 341 areillustrated like sticks (FIG. 20A). In reality, however, they arelaminated plate conductors (FIG. 21, etc.). The currents 338 flowingthrough the laminated positive busbar 315 and the laminated negativebusbar 317 are in opposite direction to each other with almost samemagnitude, cancel the magnetic flux of each other out, and result inreduction in inductance.

The current flow in the substantial circle induces the eddy current 340which flows on the metal board 304 as shown in FIG. 20C. The magneticflux is generated again by the eddy current 340 and cancels out themagnetic flux generated by the current flow in the substantial circle.So, the inductance of the current flow in the substantial circle isreduced. The juxtaposition of the junctions 339 and 341 makes theinduced current flow more on the metal board 304 and reduces theinductance more in comparison to the junctions 339 and 341 placeddistantly.

The parallel placement of the conductors and the current in oppositedirections, in addition to the reduction in the inductance related tothe chip placement, reduce the inductance generated between the DCpositive and negative terminals 314 and 316 and the junctions 339 and341, resulting in reduction in the inductance of the entire power module300 related to the recovery current.

FIG. 20B shows the upper and lower arms series circuit 150 for one ofthe three phases of the inverter circuit. Since the upper arm IGBT 328and the lower arm IGBT 330 do not conduct electricity at the same time,short-circuit current does not flow through the upper and lower IGBTs.However, the recovery current flows through the diodes 156 and 166.Since the recovery current flows reversely to polarity of the diodes,the recovery current is generated on the series circuits between the DCpositive terminal 314 and the DC negative terminal 316 made up of thediode and either the upper IGBT 328 and the lower IGBT 330 which is in aconduction state. Reduction in the inductance on the entire seriescircuits between the DC positive terminal 314 and the DC negativeterminal 316 contributes to reduction in negative effect of the spikevoltage caused by the switching operation of the inverter. Theconfiguration in FIG. 20A enables the inductance to be reduced.

Reduction in the inductance and heat of the semiconductor module inaccordance with the present embodiment will be further described.Transient voltage rise or heat generation from the semiconductor chipsis generated during switching operation of the upper or lower arm whichmakes up the inverter circuit. Therefore, a period of time for theswitching operation should preferably be shortened in accordance withreduction in inductance at the switching operation and the spikevoltage. It should be implemented not only measures for change of thecurrent that flows the switching devices including the IGBTs as spikevoltage at the switching operation but also measures for the recoverycurrent of the diodes generated at the transition. Reduction in theinductance will be detailed with an example of the recovery current ofthe diode of the lower arm.

The recovery current of the diode is a current that flows in spite ofthe reverse bias to the diode and is caused by carrier filled in thediode in forward direction to the diode. Conduction or interruption ofthe upper or lower arm, which makes up the inverter circuit, operated ina routine order results in generating three-phase AC electric power inthe AC terminals of the inverter circuit. With the switching operation,large inductance of the stator coil causes the return current to flow inthe stator coil of the motor generator via the diodes which makes up theinverter for maintaining current value. The return current is a forwardcurrent of the diode and the carrier fills inside the diode. Then, whenthe status of the semiconductor chip 328 in operation as the upper armis switched from interruption to conduction again, the recovery currentarisen from the carrier flows in the diode of the lower arm. In aroutine operation, either the upper or lower arm series circuit isinterrupted, therefore, the short-circuit current does not flow in theupper and lower arms. However, transient current, for example, therecovery current of the diode flows the series circuit made up of theupper and lower arms. The current that flows through the series circuitmay generate high spike voltage.

When the IGBT 328 which operates as the upper arm is switched on, forexample, the recovery current of the lower arm diode 166 may flow fromthe positive terminal 314 to the negative terminal 316 via the IGBT 328and the lower arm diode 166, with the IGBT 330 hereat interrupted. Theconductor between a terminal P and the junction 339 and the conductorbetween a terminal N and the junction 341 are placed parallel andwherein the same recovery current flows in opposite directions (FIG.20A). As a result, the inductance of current pathway is reduced becausethe generated magnetic fields cancel each other out in a space betweenthe conductors. The inductance is reduced because of the laminatedstructure where the conductors between the terminals are closely andopposingly placed (inductance-reduction effect by laminate effect).

The pathway for parallel current with opposite directions is followed bycircle-shaped pathway in the recovery current pathway. Current flowingthrough the circle-shaped pathway causes the eddy current 340 to flow onthe metal board 304. Effect of the eddy current for canceling themagnetic fields out causes the inductance to be reduced in thecircle-shaped pathway.

Above description includes merely the recovery current of the diode 166.The recovery current of the diode 156, however, may be generated by theconduction of the lower arm IGBT 330. Also in this case, the inductanceis reduced likewise (FIG. 20B). In the case of using ametal-oxide-semiconductor transistor (MOS transistor) in place of theIGBT, although any diode is not apparently used, in fact the diode 156or 166 exists in the MOS transistor, therefore the same phenomena asthat mentioned above is seen. The above-mentioned operations andadvantageous effects can be achieved with configurations shown in FIG.20 or the other Figs. in the case of using the MOS transistor.

With configuration of the circuit of the semiconductor module inaccordance with the present, embodiment, effects of the laminatedstructure and the eddy current reduce the inductance. Reduction ininductance at the switching operation is significant. The semiconductormodule in accordance with the present embodiment contains the seriescircuits of the upper and lower arms inside the semiconductor moduleitself. The inductance-reduction effect in the transient status is thusremarkable, for example, the reduction in the inductance to the recoverycurrent of the diode flowing through the upper and lower arms seriescircuit. Reduction in inductance realizes low induced current generatedby the semiconductor module, low-loss circuit configuration, andimproved switching speed which results in reduced period of heatgeneration.

The connections between the DC positive terminal 314 and the DC negativeterminal 316 of the power module 300 are bent in the opposite directionto each other (FIGS. 6, 13, 15, and 21). The internal surfaces of thelaminated structure are exposed to make up the connecting surfaces withother DC lines. This configuration is highly effective in theinductance-reduction of the connections, and is detailed hereinafter.

The capacitor module 500 in accordance with the present embodimentincludes advantageous effects in the inductance-reduction, raisedproductivity, and great cooling effect.

The capacitor module 500 will be hereinafter detailed with reference toFIGS. 22 to 26. FIG. 22 is a perspective view of the externalconfiguration of the capacitor module 500 which relates to the presentembodiment. FIG. 23 is a top perspective view that illustrates theconnection between the capacitor module 500 and the power modules 300.FIG. 24 is a view that shows the connection which reduces theinductance. FIG. 25 is a perspective view that shows the capacitormodule 500 before a filling material 522 such as resin is filled. FIG.26 is a detailed structure of the capacitor module 500 showing theconfiguration of the capacitor cells 514 fixed to the laminated busbar.

In FIGS. 22 to 26, components are numbered as follows: capacitor module500; capacitor case 502; negative terminals 504; positive terminals 506;DC (battery) negative connecting terminal 510; DC (battery) positiveconnecting terminal 512; positive terminal for auxiliaries 532; negativeterminal for auxiliaries 534; and, capacitor cells 514, respectively.

A plurality of sets, four sets in accordance with the presentembodiment, of the laminated busbar made up of the negative busbar 505and the positive busbar 507 are electrically connected in parallel tothe DC (battery) negative connecting terminal 510 and the DC (battery)positive connecting terminal 512. The negative busbar 505 and thepositive busbar 507 are provided with a plurality of the terminals 516and 518 for each positive terminal and each negative terminal of aplurality of the capacitor cells 514 to be connected in parallel (FIGS.25 and 26).

Each of the capacitor cells 514, which is an unit structure of storagesection of the capacitor module 500, is provided with the film capacitor515 which includes two kinds of conductive films—films for the positiveand negative terminals—sandwiching an insulating film and wound. Thefilm capacitor 515 with winding structure is provided with a positiveterminal conductive material 508 which is electrically connected to thepositive film on one end and a negative terminal conductive material 508which is electrically connected to the negative film on the other end.The negative terminal conductive material 508 is hidden in the givenFigs. The positive and negative terminals conductive materials 508 aresoldered or deposited to each of the wound films respectively.

Both the negative busbar 505 and the positive busbar 507 have thelaminated structure. Planar shape of the lamination layer made up of thenegative busbar 505 and the positive busbar 507 is long and thinsubstantially rectangular parallelepiped. Width of the plane (length ofa short side of the plane) is substantially similar to length of thecapacitor cell 514 in the winding axis direction. The terminals 516 and518 are respectively provided at both ends of the short sides of thelamination layer made up of the negative busbar 505 and the positivebusbar 507. The terminals 516 and 518 of the negative side are hidden inFIG. 26. The terminals 516 and 518, which are provided at the both endsof the lamination layer made up of the negative busbar 505 and thepositive busbar 507, are respectively soldered or welded to theconductive materials 508 at both ends of the two capacitor cells 514placed parallel to each other.

As described above, one lateral surface of the wound film capacitor 515is a positive electrode (surface of the capacitor on which the terminals516 and 518 are fixed is a positive electrode), while the oppositelateral surface is a negative electrode. The film capacitor 515 isplaced on the planar surface of the laminated busbar from both of thenegative busbar 505 and the positive busbar 507. An example of the twofilm capacitors 515 placed along the long side of the laminated busbaris given in accordance with the present embodiment.

Four cell groups are arranged in parallel, with each cell groupscomposed of the two capacitor cells 514. A total of eight capacitorcells 514 are provided as shown in FIG. 25. One lateral surface of eachof the two cells is a positive electrode. This positive electrode isconnected to the positive busbar 507 which leads to the positiveterminal 506 via either the terminal 516 or 518. The other lateralsurface of the capacitor cell 514 is a negative electrode. This negativeelectrode is connected to the negative busbar 505, which is coupled withthe positive busbar 507 across the insulation sheet 517, and led to thenegative terminal 504. As shown in FIG. 26, the positive busbar 507 isconnected to the DC (battery) positive connecting terminal 512, whilethe negative busbar 505 is connected to the DC (battery) negativeconnecting terminal 510, leading to the battery eventually.

The positive terminals of the capacitor cells 514 are linked to thepositive terminal 506 via the terminals 516 and 518 and the positivebusbar 507 (FIG. 26). The negative terminals of the capacitor cells 514are linked to the negative terminal 504 via the terminals (back side inFIG. 26) and the negative busbar 505. FIG. 26 shows for one pair of thecapacitor terminals 504 and 506, the two capacitor cells 514 areconnected in parallel. Even though four pairs of the capacitor terminals504 and 506 are provided in the example of the Figs., any number of thecapacitor cells and any number of the cell groups may be provideddepending on capacity. The terminals 504 and 506 are provided withopenings 509 and 511, respectively, to be directly screwed to the DCpositive and negative terminals 314 and 316 of the power module 300respectively.

A process for producing the capacitor module 500 will be described asfollows. The film capacitor 515 is produced by winding the films for thepositive and negative terminals around the insulation sheet. Thecapacitor cell 514 is produced by fixing the conductive material 508electrically connected to the positive and negative terminals at theboth ends of the film capacitor 515.

The plane laminated busbar provided with the terminals 516 and 518 isproduced. The laminated busbar is integrally provided with the positiveterminal 506 and the negative terminal 504 extending upright. Thelaminated busbar is provided with the substantially rectangular planewhose width is substantially equal to the length in the winding axisdirection of the film capacitor 515 and whose length in the longitudinaldirection is substantially equal to the length of the film capacitor 515placed in parallel. The plane is provided with a plurality of thecapacitor cells 514 arranged in parallel so that the outer circumferencesurfaces of the capacitor cells 514 face each other. The groups of thecells shown in FIG. 26 are produced by connecting the both ends of eachof the cells to the terminals 516 or 158. The groups of the cells aremachinable integrally with the positive terminal 506 and the positivebusbar 507, and likewise, machinable integrally with the negativeterminal 504 and the negative busbar 505. It is possible to mechanicallymake these busbars laminated with the thin insulation sheet sandwichedbetween the busbars. A plurality of the capacitor cells 514 are easilyconnected to the terminals 516 or 518 by use of machine because theterminals 516 or 518 are not surrounded by anything that hinders theproduction.

The capacitor case 502 having the terminal cover 520 is made of, forexample, metal material with high heat conduction. The plurality of thegroups of the capacitor cells are inserted into the capacitor case 502.Each of the capacitor cells 514 is arranged on the inside bottom of themetal capacitor case 502 with the outer circumference surfaces of thecapacitor cell 514 facing each other. The capacitor module 500 shown inFIG. 22 is produced by inserting predetermined groups of the capacitorcells as shown in FIG. 25 and filling with the filling material 522 madeof insulating resin. The capacitor cells are produced by groups. Thegroup of the capacitor cells are inserted into the capacitor case 502 asrequired. The number of the groups of the capacitor cells to be used ischanged depending on a model of a vehicle. The group of the capacitorcells are thus commonly usable.

Regardless of the difference in specifications of the capacitor module500 according to the model, the group of the capacitor cells can becommonly used. As mentioned above, the group of the capacitor cells arehigh in productivity.

The outer circumference of the capacitor cell 514 is arranged veryclosely to the inner surface of the capacitor case 502. The heatgenerated by the capacitor cells 514 can be transferred through thecapacitor case 502. The capacitor module 500 in accordance with thepresent embodiment has good heat transfer characteristics. As shown inFIG. 8, the heat is transferred from the capacitor case 502, which isheld by the lower cover 16, to the coolant passage 19 via the lowercover 16 and the chassis 12.

The capacitor module 500 is provided with not only the positive terminal506 and the negative terminal 504 but also the positive terminal forauxiliaries 532 and the negative terminal for auxiliaries 534. Each ofthese terminals are electrically connected with the DC (battery)positive connecting terminal 512 and the DC (battery) negativeconnecting terminal 510. The terminals for auxiliaries enable thecapacitor module 500 to be used for auxiliaries at the same time. AC canbe output not only for vehicle driving but also for other auxiliaries.Thus, overall function of the power inverter is improved.

The capacitor case 502 is provided with the terminal cover 502 whichprotects the negative terminals 504 and the positive terminals 506 inmanufacturing process or in transit of the capacitor module 500,resulting in improvement in reliability and productivity.

The connection between the power modules and the capacitor module in thepower inverter in accordance with the present embodiment will behereinafter described with reference to FIG. 23. FIG. 23 is a topperspective view illustrating the connection between the power modulesand the capacitor module which relate to the present embodiment.

The capacitor case 502 fixed on the lower cover contains a number of thecapacitor cells 514. The negative and positive capacitor terminals 504and 506 are arranged along the one side of the capacitor case 502. Theaforementioned side of the capacitor case 502 is erected in accordancewith the capacitor terminals 504 and 506 placed in the upright positionabove the top of the capacitor cells 514.

The DC negative and positive terminals 314 and 316 of the power module300 shown in FIGS. 13 and 15 are arranged to face the capacitorterminals 504 and 506. Mounting the power modules 300 on the capacitor500 enables the ends of the DC negative and positive terminals 314 and316 to be placed to directly face the capacitor terminals 504 and 506without any other connecting members.

As shown in FIGS. 13 and 15, the DC positive terminals 314 and the DCnegative terminals 316 of the power module 300 protrude from the powermodule case 502. As illustrated in FIG. 22, the positive terminals 506and the negative terminals 504 stand upright in a L-shape beyond thesurface of the filling material 522 for the capacitor cells from thelateral side. At assembly of the power inverter, the capacitor terminals504 and 506 with the L-structure come into direct contact with the DCterminals 314 and 316 of the power modules 300, which protrude from thepower module case 302. The capacitor terminals 504 and 506 and the DCterminal 314 and 316 are bolted together.

While large inductance may be generated at connection between theterminals, the terminal configuration of the power module 300 and thecapacitor module 500 in accordance with the present invention enablesinductance to be reduced. Reduction in inductance will be described withreference to FIG. 24.

FIG. 24 shows the flow of electric current at the connection between thenegative terminal 504 or the positive capacitor 506 and the DC negativeterminal 316 or the DC positive terminal 314 of the power module 300.The negative terminal 504 and the positive terminal 506, and the DCnegative terminal 316 and the DC positive terminal 314 are each made upof laminated conductor parts which sandwich the thin insulation memberand coupling parts for connecting with the corresponding terminals. Theends of the conductor parts are bent in opposite directions to eachother. The internal surface of the laminated structure is exposed tomake up the connecting surface for connecting with the correspondingterminal.

The connecting surface extends to right and left around the laminatedstructure as a center (FIG. 24). The exposed connecting surfaces arecontacted with each other. The electric current flows through thepositive and negative busbars via the contacting surface. The flow ofthe current on the positive terminal 618 and the flow of the current onthe negative terminal 620 are illustrated in FIG. 24. Even thoughdistribution of the current on the contacting surface may vary dependingon conditions of the contacting surface, the current which flows fromthe central laminated part and through right and left on the contactingsurface, returns to the central laminated part. The magnitude and thedirection of the electrical current flowing right and left and theelectrical current returning to the central laminated part after passingthrough the contacting surface are equal and opposite respectively.Therefore, the magnetic fluxes generated by each current cancel eachother out. Thus, the inductance of the connection is greatly reduced.

It is not preferable for the inductance of the connection to be largewhile the inductance of busbar is small. According to the presentembodiment, the configuration shown in FIG. 24 reduces the inductance ofthe connection. It is most preferable that in accordance with thepresent embodiment the DC terminal of the power module 300 is directlyconnected with the DC terminal of the capacitor module 500. Theinductance of the connection, however, is reduced not only by directconnection but also by using other laminated connection conductor.

In accordance with the present embodiment, the direct connection betweenthe terminals of the capacitor 500 and the power module 300 enables thenumber of the components to be decreased, assembly workability to beimproved, and miniaturization to be realized. In accordance with thepresent embodiment, furthermore, removing the floating inductance by theintermediate member which connects between the terminals of conventionalcapacitor module and power module achieves reduction in the spikevoltage and improvement in reliability of the power inverter.

As the above description with reference to the FIG. 24, in accordancewith the present embodiment, the connection splits into oppositedirections to each other. And, the current flow turns near theconnecting surface with the other conductor. Therefore, the magneticfluxes by each current cancel each other out near the connectingsurface. Thus, the inductance of the connection is greatly reduced. Theterminal connection having this structure reduces the inductance of theconnection. Therefore, it is most preferable that the DC terminals ofthe power module 300 and of the capacitor module 500 are directlyconnected with each other. The inductance of the overall circuit,however, can be reduced even if other laminated busbar is used betweenboth terminals.

As described above, in accordance with embodiments of the presentinvention, the inductance of the smoothing capacitor and the invertercircuit will be reduced. At the same time, the volume of the powerinverter will be reduced. And, the maximum conversion electric powervalue per unit volume of the power inverter will be increased.

The above-described embodiments are examples, and various modificationscan be made without departing from the scope of the invention.

What is claimed is:
 1. A power inverter, comprising: a first powermodule having a plurality of switching devices, and a DC terminal; asecond power module having a plurality of switching devices; acapacitor; a positive busbar connecting an electrode of the capacitor toa first side of the DC terminal of the first power module; a negativebusbar connecting the other electrode of the capacitor to a second sideof the DC terminal of the first power module; a coolant portion having acoolant passage; a chassis that houses the first and second powermodules, the capacitor, the positive busbar, the negative busbar, andthe coolant portion; a capacitor module that smoothes DC electricity andsupplies smoothed DC electricity to the first power module and thesecond power module; a control circuit board controlling a switching ofthe switching device of the first power module; a base plate on whichthe control circuit board is mounted; and a lower case; wherein: amaximum conversion electric power of the second power module is smallerthan a maximum conversion electric power of the first power module; aninterior portion of the chassis is divided into a first region and asecond region; the first power module is disposed in the first region;the second power module is disposed in the second region; the capacitoris disposed in the second region; the positive busbar and the negativebusbar cross a space between the first region and the second region; thecapacitor module is disposed at a cover for covering an opening formedat the second region, and a heat conduction passage is formed betweenthe cover and the capacitor module; the second power module is disposedin the second region at the coolant passage while keeping apredetermined space between the second power module and the capacitormodule, and auxiliary power module terminals extend from the capacitormodule and are connected to the second power module across thepredetermined space; the chassis has a first opening facing the firstregion and a second opening facing of the second region; the base plateis fixed to the chassis so that the base plate covers the first opening;the lower case is fixed to the chassis so that the lower case covers thesecond opening; and the capacitor is disposed on the lower case.
 2. Apower inverter according to claim 1, wherein: the coolant portion isdisposed on the chassis so that it divides the interior portion of thechassis between the first region and second region.
 3. A power inverteraccording to claim 1, wherein: the first power module is disposed on thecoolant portion; and the second power module is disposed on the coolantportion.
 4. A power inverter according to claim 1, wherein: a space islocated between a side of the coolant portion and the chassis.
 5. Apower inverter according to claim 1, further comprising: an insulationsheet disposed between the positive busbar and the negative busbar,wherein the portions of the positive busbar and the negative busbarcrossing the space between the first and second regions are laminatedwith the insulation sheet.
 6. A power inverter according to claim 1,wherein: the second power module has a DC terminal connected with thecapacitor.
 7. A power inverter according to claim 1, wherein: the firstpower module has a metal board on which the semiconductor device ismounted; the coolant portion has an opening that leads to the coolantpassage; and the metal board is fixed to the coolant portion so that themetal board closes the opening.
 8. A power inverter according to claim7, wherein: the metal board has a fin that protrudes from the opening tothe coolant passage.
 9. A power inverter according to claim 1, wherein:the chassis has an opening at a side of the first region; and the baseplate is fixed to the chassis so that the base plate covers the openingat the side of the first region.
 10. A power inverter according to claim1, wherein: the chassis has an opening at a side of the second region;the lower case is fixed to the chassis so that the lower case covers theopening; and the capacitor is disposed on the lower case.
 11. A powerinverter according to claim 1, further comprising: an inlet pipe linkedto the coolant passage; and an outlet pipe linked to the coolantpassage; wherein: the inlet and outlet pipes connect with the chassis.